 |
|
||||||||||
Publications of M. Troyer
Multiorbital Kondo physics of Co in Cu hosts
,
Surer, Brigitte, Troyer, Matthias, Werner, Matthias, Wehling, Tim O., Läuchli, Andreas M., Wilhelm, Aljoscha, Lichtenstein, Alexander I.,
2012
>>
| Author(s): | Surer, Brigitte, Troyer, Matthias, Werner, Matthias, Wehling, Tim O., Läuchli, Andreas M., Wilhelm, Aljoscha, Lichtenstein, Alexander I. |
| Title: | Multiorbital Kondo physics of Co in Cu hosts |
| Abstract: | We investigate the electronic structure of cobalt atoms on a copper surface and in a copper host by combining density-functional calculations with a numerically exact continuous-time quantum Monte Carlo treatment of the five-orbital impurity problem. In both cases we find low energy resonances in the density of states of all five Co d orbitals. The corresponding self-energies indicate the formation of a Fermi liquid state at low temperatures. Our calculations yield the characteristic energy scale-the Kondo temperature-for both systems in good agreement with experiments. We quantify the charge fluctuations in both geometries and suggest that Co in Cu must be described by an Anderson impurity model rather than by a model assuming frozen impurity valency at low energies. We show that fluctuations of the orbital degrees of freedom are crucial for explaining the Kondo temperatures obtained in our calculations and measured in experiments. |
| Published in: | Physical Review B |
| Volume: | 85 |
| Issue: | 8 |
| Pages: | 085114 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Werkstoffprüfung und -eigenschaften|Materials Testing, Properties, Kondensierte Materie|Condensed Matter |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000300566600005 |
| DOI: | 10.1103/PhysRevB.85.085114 |
| Nebis system number: | 001888782 |
Galois Conjugates of Topological Phases
,
Freedman, Michael H., Gukelberger, Jan, Hastings, Matthew B., Trebst, Simon, Troyer, Matthias, Wang, Zhenghan,
2012
>>
| Author(s): | Freedman, Michael H., Gukelberger, Jan, Hastings, Matthew B., Trebst, Simon, Troyer, Matthias, Wang, Zhenghan |
| Title: | Galois Conjugates of Topological Phases |
| Abstract: | Galois conjugation relates unitary conformal field theories (CFTs) and topological quantum field theories (TQFTs) to their non-unitary counterparts. Here we investigate Galois conjugates of quantum double models, such as the Levin-Wen model. While these Galois conjugated Hamiltonians are typically non-Hermitian, we find that their ground state wave functions still obey a generalized version of the usual code property (local operators do not act on the ground state manifold) and hence enjoy a generalized topological protection. The key question addressed in this paper is whether such non-unitary topological phases can also appear as the ground states of Hermitian Hamiltonians. Specific attempts at constructing Hermitian Hamiltonians with these ground states lead to a loss of the code property and topological protection of the degenerate ground states. Beyond this we rigorously prove that no local change of basis can transform the ground states of the Galois conjugated doubled Fibonacci theory into the ground states of a topological model whose Hermitian Hamiltonian satisfies Lieb-Robinson bounds. These include all gapped local or quasi-local Hamiltonians. A similar statement holds for many other non-unitary TQFTs. One consequence is that the "Gaffnian" wave function cannot be the ground state of a gapped fractional quantum Hall state. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 85 |
| Issue: | 4 |
| Pages: | 045414 |
| ISSN: | 0556-2805, 0163-1829, 1098-0121, 1550-235X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325077585, WOS-000298922300010 |
| DOI: | 10.1103/PhysRevB.85.045414 |
Three-sublattice order in the SU(3) Heisenberg model on the square and triangular lattice
,
Bauer, Bela, Corboz, Philippe, Läuchli, Andreas M., Messio, Laura, Penc, Karlo, Troyer, Matthias, Mila, Frédéric,
2012
>>
| Author(s): | Bauer, Bela, Corboz, Philippe, Läuchli, Andreas M., Messio, Laura, Penc, Karlo, Troyer, Matthias, Mila, Frédéric |
| Title: | Three-sublattice order in the SU(3) Heisenberg model on the square and triangular lattice |
| Abstract: | We present a numerical study of the SU(3) Heisenberg model of three-flavor fermions on the triangular and square lattice by means of the density-matrix renormalization group and infinite projected entangled-pair states. For the triangular lattice we confirm that the ground state has a three-sublattice order with a finite ordered moment which is compatible with the result from linear flavor wave theory (LFWT). The same type of order has recently been predicted also for the square lattice [T. A. Toth et al., Phys. Rev. Lett. 105, 265301 (2010)] from LFWT and exact diagonalization. However, for this case the ordered moment cannot be computed based on LFWT due to divergent fluctuations. Our numerical study clearly supports this three-sublattice order, with an ordered moment of m = 0.2-0.4 in the thermodynamic limit. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 85 |
| Issue: | 12 |
| Pages: | 125116 |
| ISSN: | 0556-2805, 0163-1829, 1098-0121, 1550-235X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Werkstoffprüfung und -eigenschaften|Materials Testing, Properties, Kondensierte Materie|Condensed Matter |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325530610, 001888782 |
| DOI: | 10.1103/PhysRevB.85.125116 |
Diagrammatic quantum Monte Carlo solution of the two-dimensional cooperon-fermion model
,
Yang, Kai-Yu, Kozik, E., Wang, Xin, Troyer, M.,
2011
>>
| Author(s): | Yang, Kai-Yu, Kozik, E., Wang, Xin, Troyer, M. |
| Title: | Diagrammatic quantum Monte Carlo solution of the two-dimensional cooperon-fermion model |
| Abstract: | We investigate the two-dimensional cooperon-fermion model in the correlated regime with a continuous-time diagrammatic determinant quantum Monte Carlo algorithm. We estimate the transition temperature T-c, examine the effectively reduced band gap and cooperon mass, and find that delocalization of the cooperons enhances the diamagnetism. When applied to diamagnetism of the pseudogap phase in high-T-c cuprates, we obtain results in qualitative agreement with recent torque magnetization measurements. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 83 |
| Issue: | 21 |
| Pages: | 214516 |
| ISSN: | 0163-1829, 1098-0121, 0556-2805, 1550-235X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000291652300006 |
| DOI: | 10.1103/PhysRevB.83.214516 |
| Nebis system number: | 001888782 |
Mutual information in classical spin models
,
Wilms, Johannes, Troyer, Matthias, Verstraete, Frank,
2011
>>
| Author(s): | Wilms, Johannes, Troyer, Matthias, Verstraete, Frank |
| Title: | Mutual information in classical spin models |
| Abstract: | The total many-body correlations present in finite temperature classical spin systems are studied using the concept of mutual information. As opposed to zero-temperature quantum phase transitions, the total correlations are not maximal at the phase transition, but reach a maximum in the high-temperature paramagnetic phase. The Shannon mutual information and the Renyi mutual information in both Ising and Potts models in two dimensions are calculated numerically by combining matrix product state algorithms and Monte Carlo sampling techniques. |
| Published in: | Journal of Statistical Mechanics-Theory and Experiment |
| Volume: | 2011 |
| Pages: | P10011 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Classical phase transitions (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Classical phase transitions (theory) |
| DBID source: | WOS-000296709800012 |
| DOI: | 10.1088/1742-5468/2011/10/P10011 |
| Nebis system number: | 004699119 |
Identifying Quantum Topological Phases Through Statistical Correlation
,
Wang, Hao, Bauer, Bela, Troyer, Matthias, Scarola, Vito W.,
2011
>>
| Author(s): | Wang, Hao, Bauer, Bela, Troyer, Matthias, Scarola, Vito W. |
| Title: | Identifying Quantum Topological Phases Through Statistical Correlation |
| Abstract: | We theoretically examine the use of a statistical distance measure, the indistinguishability, as a generic tool for the identification of topological order. We apply this measure to the toric code and two fractional quantum Hall models. We find that topologically ordered states can be identified with the indistinguishability for both models. Calculations with the indistinguishability also underscore a key distinction between symmetries that underly topological order in the toric code and quantum Hall models. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 83 |
| Issue: | 11 |
| Pages: | 115119 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294930511, WOS-000288318600004 |
| DOI: | 10.1103/PhysRevB.83.115119 |
| Nebis system number: | 001888782 |
Quantum spin ladders of non-Abelian anyons
,
Poilblanc, Didier, Ludwig, Andreas W.W., Trebst, Simon, Troyer, Matthias,
2011
>>
| Author(s): | Poilblanc, Didier, Ludwig, Andreas W.W., Trebst, Simon, Troyer, Matthias |
| Title: | Quantum spin ladders of non-Abelian anyons |
| Abstract: | Quantum ladder models, consisting of coupled chains, form intriguing systems bridging one and two dimensions and have been well studied in the context of quantum magnets and fermionic systems. Here we consider ladder systems made of more exotic quantum mechanical degrees of freedom, so-called non-Abelian anyons, which can be thought of as certain quantum deformations of ordinary SU(2) spins. Such non-Abelian anyons occur as quasiparticle excitations in topological quantum fluids, including p(x) + ip(y) superconductors, certain fractional quantum Hall states, and rotating Bose-Einstein condensates. Here we use a combination of exact diagonalization and conformal field theory to determine the phase diagrams of ladders with up to four chains. We discuss how phenomena familiar from ordinary SU(2) spin ladders are generalized in their anyonic counterparts, such as gapless and gapped phases, odd and even effects with the ladder width, and elementary "magnon" excitations. Other features are entirely due to the topological nature of the anyonic degrees of freedom. In general, two-dimensional systems of interacting localized non-Abelian anyons are anyonic generalizations of two-dimensional quantum magnets. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 83 |
| Issue: | 13 |
| Pages: | 134439 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000292146200002 |
| DOI: | 10.1103/PhysRevB.83.134439 |
| Nebis system number: | 001888782 |
The bosonic superfluid-insulator transition in continuous space
,
Pilati, Sebastiano, Troyer, Matthias,
2011
>>
| Author(s): | Pilati, Sebastiano, Troyer, Matthias |
| Title: | The bosonic superfluid-insulator transition in continuous space |
| Abstract: | We investigate the zero-temperature phase diagram of interacting Bose gases in the presence of a simple cubic optical lattice, going beyond the regime where the mapping to the single-band Bose-Hubbard model is reliable. Our computational approach is a new hybrid quantum Monte Carlo method which combines algorithms used to simulate homogeneous quantum fluids in continuous space with those used for discrete lattice models of strongly correlated systems. We determine the critical interaction strength and optical lattice intensity where the superfluid-to-insulator transition takes place, considering also the regime of shallow optical lattices and strong interatomic interactions. The implications of our findings for the supersolid state of matter are discussed. |
| Published in: | Physical review letters |
| Volume: | 108 |
| Issue: | 15 |
| Pages: | 155301 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| DBID source: | FORM-1324996692, WOS-000302635600009 |
| DOI: | 10.1103/PhysRevLett.108.155301 |
| Nebis system number: | 000003868 |
Two-dimensional quantum liquids from interacting non-Abelian anyons
,
Ludwig, Andreas W.W., Poilblanc, Didier, Trebst, Simon, Troyer, Matthias,
2011
>>
| Author(s): | Ludwig, Andreas W.W., Poilblanc, Didier, Trebst, Simon, Troyer, Matthias |
| Title: | Two-dimensional quantum liquids from interacting non-Abelian anyons |
| Abstract: | A set of localized, non-Abelian anyons-such as vortices in a p(x) + ip(y) superconductor or quasiholes in certain quantum Hall states-gives rise to a macroscopic degeneracy. Such a degeneracy is split in the presence of interactions between the anyons. Here, we show that in two spatial dimensions this splitting selects a unique collective state as ground state of the interacting many-body system. This collective state can be a novel gapped quantum liquid nucleated inside the original parent liquid (of which the anyons are excitations). This physics is of relevance for any quantum Hall plateau realizing a non-Abelian quantum Hall state when moving off the center of the plateau. |
| Published in: | New journal of physics |
| Volume: | 13 |
| Pages: | 045014 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000289993000006 |
| DOI: | 10.1088/1367-2630/13/4/045014 |
| Nebis system number: | 001997538 |
A Provenance-Based Infrastructure to Support the Life Cycle of Executable Papers
,
Koop, David, et al., Bauer, Bela, Surer, Brigitte, Troyer, Matthias,
2011
>>
| Author(s): | Koop, David, et al., Bauer, Bela, Surer, Brigitte, Troyer, Matthias |
| Title: | A Provenance-Based Infrastructure to Support the Life Cycle of Executable Papers |
| Abstract: | As publishers establish a greater online presence as well as infrastructure to support the distribution of more varied information, the idea of an executable paper that enables greater interaction has developed. An executable paper provides more information for computational experiments and results than the text, tables, and figures of standard papers. Executable papers can bundle computational content that allow readers and reviewers to interact, validate, and explore experiments. By including such content, authors facilitate future discoveries by lowering the barrier to reproducing and extending results. We present an infrastructure for creating, disseminating, and maintaining executable papers. Our approach is rooted in provenance, the documentation of exactly how data, experiments, and results were generated. We seek to improve the experience for everyone involved in the life cycle of an executable paper. The automated capture of provenance information allows authors to easily integrate and update results into papers as they write, and also helps reviewers better evaluate approaches by enabling them to explore experimental results by varying parameters or data. With a provenance-based system, readers are able to examine exactly how a result was developed to better understand and extend published findings. |
| Published in: | Procedia computer science |
| Volume: | 4 |
| Pages: | 648 - 657 |
| ISSN: | 1877-0509 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Executable paper, Reproducibility, Provenance, Scientific workflows |
| Event name: | International Conference on Computational Science, (ICCS) 2011 |
| Event date: | June 1-3, 2011 |
| Place: | Singapore, Republic of Singapore |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Executable paper, Reproducibility, Provenance, Scientific workflows |
| DBID source: | FORM-1327414040 |
| DOI: | 10.1016/j.procs.2011.04.068 |
| Nebis system number: | 006163977 |
Dynamics at and near conformal quantum critical points
,
Isakov, S. V., Fendley, P., Ludwig, A. W. W., Trebst, S., Troyer, M.,
2011
>>
| Author(s): | Isakov, S. V., Fendley, P., Ludwig, A. W. W., Trebst, S., Troyer, M. |
| Title: | Dynamics at and near conformal quantum critical points |
| Abstract: | We explore the dynamical behavior at and near a special class of two-dimensional quantum critical points. Each is a conformal quantum critical point (CQCP), where in the scaling limit the equal-time correlators are those of a two-dimensional conformal field theory. The critical theories include the square-lattice quantum dimer model, the quantum Lifshitz theory, and a deformed toric code model. We show that under generic perturbation the latter flows toward the ordinary Lorentz-invariant (2 + 1)-dimensional Ising critical point, illustrating that CQCPs are generically unstable. We exploit a correspondence between the classical and quantum-dynamical behavior in such systems to perform an extensive numerical study of two lines of CQCPs in a quantum eight-vertex model or, equivalently, two coupled deformed toric codes. We find that the dynamical critical exponent z remains 2 along the U(1)-symmetric quantum Lifshitz line, while it continuously varies along the line with only Z(2) symmetry. This illustrates how two CQCPs can have very different dynamical properties, despite identical equal-time ground-state correlators. Our results equally apply to the dynamics of the corresponding purely classical models. |
| Published in: | Physical review B |
| Volume: | 83 |
| Issue: | 12 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY, USA |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000288695600002 |
| DOI: | 10.1103/PhysRevB.83.125114 |
| Nebis system number: | 001888782 |
Trapped ultracold bosons in periodically modulated lattices
,
Huo, Jia-Wei, Zhang, Fu-Chun, Chen, Weiqiang, Troyer, Matthias, Schollwock, Ulrich,
2011
>>
| Author(s): | Huo, Jia-Wei, Zhang, Fu-Chun, Chen, Weiqiang, Troyer, Matthias, Schollwock, Ulrich |
| Title: | Trapped ultracold bosons in periodically modulated lattices |
| Abstract: | Motivated by the recent rapid development of the field of quantum gases in optical lattices, we present a comprehensive study of the spectrum of ultracold atoms in a one-dimensional optical lattice subjected to a periodic lattice modulation. Using the time-dependent density matrix renormalization group method, we study the dynamical response due to lattice modulations in different quantum phases of the system with varying density. For the Mott-insulating state, we identify several excitation processes, which provide important information about the density profile of the gases. For the superfluid, the dynamical response can be well described in a local density approximation. This simplification can be valuable in understanding the strong-correlated superfluid in a slow-varying harmonic potential. All these spectroscopic features of an inhomogeneous system can be used as a test for the validity of the Bose-Hubbard model in a parabolic trapping potential. |
| Published in: | Physical review. A |
| Volume: | 84 |
| Issue: | 4 |
| Pages: | ARTN 043608 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000295629100007 |
| DOI: | 10.1103/PhysRevA.84.043608 |
| Nebis system number: | 000619853 |
Continuous-time Monte Carlo methods for quantum impurity models
,
Gull, Emanuel, Millis, Andrew J., Lichtenstein, Alexander I., Rubtsov, Alexey N., Troyer, Matthias, Werner, Philipp,
2011
>>
| Author(s): | Gull, Emanuel, Millis, Andrew J., Lichtenstein, Alexander I., Rubtsov, Alexey N., Troyer, Matthias, Werner, Philipp |
| Title: | Continuous-time Monte Carlo methods for quantum impurity models |
| Abstract: | Quantum impurity models describe an atom or molecule embedded in a host material with which it can exchange electrons. They are basic to nanoscience as representations of quantum dots and molecular conductors and play an increasingly important role in the theory of "correlated electron" materials as auxiliary problems whose solution gives the "dynamical mean-field" approximation to the self-energy and local correlation functions. These applications require a method of solution which provides access to both high and low energy scales and is effective for wide classes of physically realistic models. The continuous-time quantum Monte Carlo algorithms reviewed in this article meet this challenge. Derivations and descriptions of the algorithms are presented in enough detail to allow other workers to write their own implementations, discuss the strengths and weaknesses of the methods, summarize the problems to which the new methods have been successfully applied, and outline prospects for future applications. |
| Published in: | Reviews of modern physics |
| Volume: | 83 |
| Issue: | 2 |
| Pages: | 349 - 404 |
| ISSN: | 0034-6861 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Minneapolis, Minn. |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000290254100001 |
| DOI: | 10.1103/RevModPhys.83.349 |
| Nebis system number: | 000053843 |
Spectral properties of the three-dimensional Hubbard model
,
Fuchs, Sebastian, Gull, Emanuel, Troyer, Matthias, Jarrell, Mark, Pruschke, Thomas,
2011
>>
| Author(s): | Fuchs, Sebastian, Gull, Emanuel, Troyer, Matthias, Jarrell, Mark, Pruschke, Thomas |
| Title: | Spectral properties of the three-dimensional Hubbard model |
| Abstract: | We present momentum-resolved single-particle spectra for the three-dimensional Hubbard model for the paramagnetic and antiferromagnetically ordered phase obtained within the dynamical cluster approximation. The effective cluster problem is solved by continuous-time quantum Monte Carlo simulations. The absence of a time discretization error and the ability to perform Monte Carlo measurements directly in Matsubara frequencies enable us to analytically continue the self-energies by maximum entropy, which is essential to obtaining momentum-resolved spectral functions for the Neel state. We investigate the dependence on temperature and interaction strength and the effect of magnetic frustration introduced by a next-nearest-neighbor hopping. One particular question we address here is the influence of the frustrating interaction on the metal-insulator transition of the three-dimensional Hubbard model. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 83 |
| Issue: | 23 |
| Pages: | 235113 |
| ISSN: | 0163-1829, 1098-0121, 0556-2805, 1550-235X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Physik und Astronomie|Physics and Astronomy |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000291351900005 |
| DOI: | 10.1103/PhysRevB.83.235113 |
| Nebis system number: | 001888782 |
Thermodynamics of the 3D Hubbard Model on Approaching the Néel Transition
,
Fuchs, Sebastian, Gull, Emanuel, Pollet, Lode, Burovski, Evgeni, Kozik, Evgeny, Pruschke, Thomas, Troyer, Matthias,
2011
>>
| Author(s): | Fuchs, Sebastian, Gull, Emanuel, Pollet, Lode, Burovski, Evgeni, Kozik, Evgeny, Pruschke, Thomas, Troyer, Matthias |
| Title: | Thermodynamics of the 3D Hubbard Model on Approaching the Néel Transition |
| Abstract: | We study the thermodynamic properties of the 3D Hubbard model for temperatures down to the Néel temperature by using cluster dynamical mean-field theory. In particular, we calculate the energy, entropy, density, double occupancy, and nearest-neighbor spin correlations as a function of chemical potential, temperature, and repulsion strength. To make contact with cold-gas experiments, we also compute properties of the system subject to an external trap in the local density approximation. We find that an entropy per particle S/N≈0.65(6) at U/t=8 is sufficient to achieve a Néel state in the center of the trap, substantially higher than the entropy required in a homogeneous system. Precursors to antiferromagnetism can clearly be observed in nearest-neighbor spin correlators. |
| Published in: | Physical review letters |
| Volume: | 106 |
| Issue: | 3 |
| Pages: | 030401 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1327413593 |
| DOI: | 10.1103/PhysRevLett.106.030401 |
| Nebis system number: | 000003868 |
Topological phases
,
Freedman, Michael H., Gamper, Lukas, Gils, Charlotte, Isakov, Sergei V., Trebst, Simon, Troyer, Matthias,
2011
>>
| Author(s): | Freedman, Michael H., Gamper, Lukas, Gils, Charlotte, Isakov, Sergei V., Trebst, Simon, Troyer, Matthias |
| Title: | Topological phases |
| Subtitle: | An expedition off lattice |
| Abstract: | Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of 'baby universe', here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger's theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically. |
| Published in: | Annals of physics |
| Volume: | 326 |
| Issue: | 8 |
| Pages: | 2108 - 2137 |
| ISSN: | 0003-4916, 1096-035X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Statistical mechanics, Topological phases |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Statistical mechanics, Topological phases |
| DBID source: | WOS-000291910800014 |
| DOI: | 10.1016/j.aop.2011.03.005 |
| Nebis system number: | 000042350 |
Stripes in the two-dimensional t-J model with infinite projected entangled-pair states
,
Corboz, Philippe, White, Steven R., Vidal, Guifré, Troyer, Matthias,
2011
>>
| Author(s): | Corboz, Philippe, White, Steven R., Vidal, Guifré, Troyer, Matthias |
| Title: | Stripes in the two-dimensional t-J model with infinite projected entangled-pair states |
| Abstract: | We simulate the t-J model in two dimensions by means of infinite projected entangled-pair states (iPEPS) generalized to arbitrary unit cells, finding results similar to those previously obtained by the density-matrix renormalization group (DMRG) for wide ladders. In particular, we show that states exhibiting stripes, that is, a unidirectional modulation of hole-density and antiferromagnetic order with a p-phase shift between adjacent stripes, have a lower variational energy than uniform phases predicted by variational and fixed-node Monte Carlo simulations. For a fixed unit-cell size the energy per hole is minimized for a hole density rho(l) similar to 0.5 per unit length of a stripe. The superconducting order parameter is maximal around rho(l) similar to 0.75-0.8. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 84 |
| Issue: | 4 |
| Pages: | 041108 |
| ISSN: | 1098-0121, 0163-1829, 0556-2805, 1550-235X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000293305100001 |
| DOI: | 10.1103/PhysRevB.84.041108 |
| Nebis system number: | 001888782 |
Simultaneous Dimerization and SU(4) Symmetry Breaking of 4-Color Fermions on the Square Lattice
,
Corboz, Philippe, Lauchli, Andreas M., Penc, Karlo, Troyer, Matthias, Mila, Frédéric,
2011
>>
| Author(s): | Corboz, Philippe, Lauchli, Andreas M., Penc, Karlo, Troyer, Matthias, Mila, Frédéric |
| Title: | Simultaneous Dimerization and SU(4) Symmetry Breaking of 4-Color Fermions on the Square Lattice |
| Abstract: | Using infinite projected entangled-pair states, exact diagonalization, and flavor-wave theory, we show that the SU(4) Heisenberg model undergoes a spontaneous dimerization on the square lattice, in contrast with its SU(2) and SU(3) counterparts, which develop Neel and three-sublattice stripelike long-range order. Since the ground state of a dimer is not a singlet for SU(4) but a 6-dimensional irreducible representation, this leaves the door open for further symmetry breaking. We provide evidence that, unlike in SU(4) ladders, where dimers pair up to form singlet plaquettes, here the SU(4) symmetry is additionally broken, leading to a gapless spectrum in spite of the broken translational symmetry. |
| Published in: | Physical Review Letters |
| Volume: | 107 |
| Issue: | 21 |
| Pages: | 215301 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000297135600008 |
| DOI: | 10.1103/PhysRevLett.107.215301 |
| Nebis system number: | 000003868 |
The ALPS project release 2.0
,
Bauer, Bela, et al., Gamper, Lukas, Gukelberger, Jan, Hehn, Markus, Isakov, Sergei V., Ma, Ping Nang, Mates, P., Pollet, Lode Corneel, Surer, Brigitte, Troyer, Matthias, Werner, Philipp,
2011
>>
| Author(s): | Bauer, Bela, et al., Gamper, Lukas, Gukelberger, Jan, Hehn, Markus, Isakov, Sergei V., Ma, Ping Nang, Mates, P., Pollet, Lode Corneel, Surer, Brigitte, Troyer, Matthias, Werner, Philipp |
| Title: | The ALPS project release 2.0 |
| Subtitle: | Open source software for strongly correlated systems |
| Abstract: | We present release 2.0 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. The code development is centered on common XML and HDF5 data formats, libraries to simplify and speed up code development, common evaluation and plotting tools, and simulation programs. The programs enable non-experts to start carrying out serial or parallel numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), the density matrix renormalization group (DMRG) both in a static version and a dynamic time-evolving block decimation (TEBD) code, and quantum Monte Carlo solvers for dynamical mean field theory (DMFT). The ALPS libraries provide a powerful framework for programmers to develop their own applications, which, for instance, greatly simplify the steps of porting a serial code onto a parallel, distributed memory machine. Major changes in release 2.0 include the use of HDF5 for binary data, evaluation tools in Python, support for the Windows operating system, the use of CMake as build system and binary installation packages for Mac OS X and Windows, and integration with the VisTrails workflow provenance tool. The software is available from our web server at http://alps.comp-phys.org/. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2011 |
| Issue: | 5 |
| Pages: | P05001 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Density matrix renormalization group calculations, Classical Monte Carlo simulations, Quantum Monte Carlo simulations, Quantum phase transitions (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Density matrix renormalization group calculations, Classical Monte Carlo simulations, Quantum Monte Carlo simulations, Quantum phase transitions (theory) |
| DBID source: | WOS-000292190200002 |
| DOI: | 10.1088/1742-5468/2011/05/P05001 |
| Nebis system number: | 004699119 |
Implementing global Abelian symmetries in projected entangled-pair state algorithms
,
Bauer, Bela, Corboz, Philippe, Orús, Román, Troyer, Matthias,
2011
>>
| Author(s): | Bauer, Bela, Corboz, Philippe, Orús, Román, Troyer, Matthias |
| Title: | Implementing global Abelian symmetries in projected entangled-pair state algorithms |
| Abstract: | Due to the unfavorable scaling of tensor-network methods with the refinement parameter M, new approaches are necessary to improve the efficiency of numerical simulations based on such states, in particular for gapless, strongly entangled systems. In one-dimensional density matrix renormalization group methods, the use of Abelian symmetries has led to large computational gain. In higher-dimensional tensor networks, this is associated with significant technical efforts and additional approximations. We explain a formalism to implement such symmetries in two-dimensional tensor-network states and present benchmark results that confirm the validity of these approximations in the context of projected entangled-pair state algorithms. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 83 |
| Issue: | 12 |
| Pages: | 125106 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294930413, WOS-000288532400002 |
| DOI: | 10.1103/PhysRevB.83.125106 |
| Nebis system number: | 001888782 |
Microscopic models of interacting Yang-Lee anyons
,
Ardonne, Eddy, Gukelberger, Jan, Ludwig, Andreas W.W., Trebst, Simon, Troyer, Matthias,
2011
>>
| Author(s): | Ardonne, Eddy, Gukelberger, Jan, Ludwig, Andreas W.W., Trebst, Simon, Troyer, Matthias |
| Title: | Microscopic models of interacting Yang-Lee anyons |
| Abstract: | Collective states of interacting non-Abelian anyons have recently been studied mostly in the context of certain fractional quantum Hall states, such as the Moore-Read state proposed to describe the physics of the quantum Hall plateau at filling fraction v = 5/2. In this manuscript, we further expand this line of research and present non-unitary generalizations of interacting anyon models. In particular, we introduce the notion of Yang-Lee anyons, discuss their relation to the so-called `Gaffnian' quantum Hall wave function, and describe an elementary model for their interactions. A one-dimensional version of this model -- a non-unitary generalization of the original golden chain model -- can be fully understood in terms of an exact algebraic solution and numerical diagonalization. We discuss the gapless theories of these chain models for general su(2)_k anyonic theories and their Galois conjugates. We further introduce and solve a one-dimensional version of the Levin-Wen model for non-unitary Yang-Lee anyons. |
| Published in: | New journal of physics |
| Volume: | 13 |
| Issue: | 4 |
| Pages: | 045006 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294427815 |
| DOI: | 10.1088/1367-2630/13/4/045006 |
| Nebis system number: | 001997538 |
Dynamical mean-field theory for bosons
,
Anders, P., Gull, E., Pollet, L., Troyer, M., Werner, P.,
2011
>>
| Author(s): | Anders, P., Gull, E., Pollet, L., Troyer, M., Werner, P. |
| Title: | Dynamical mean-field theory for bosons |
| Abstract: | We discuss the recently developed bosonic dynamical mean-field theory (B-DMFT) framework, which maps a bosonic lattice model onto the self-consistent solution of a bosonic impurity model with coupling to a reservoir of normal and condensed bosons. The effective impurity action is derived in several ways: (i) as an approximation to the kinetic energy functional of the lattice problem, (ii) using a cavity approach and (iii) using an effective medium approach based on adding a one-loop correction to the self-consistently defined condensate. To solve the impurity problem, we use a continuous-time Monte Carlo algorithm based on the sampling of a perturbation expansion in the hybridization functions and the condensate wave function. As applications of the formalism, we present finite-temperature B-DMFT phase diagrams for the bosonic Hubbard model on a three-dimensional (3D) cubic and a 2D square lattice, the condensate order parameter as a function of chemical potential, critical exponents for the condensate, the approach to the weakly interacting Bose gas regime for weak repulsions and the kinetic energy as a function of temperature. |
| Published in: | New journal of physics |
| Volume: | 13 |
| Pages: | 075013 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General, Electronic-structure calculations, Quantum impurity models, Monte-carlo, Infinite dimensions, Anderson model, Mott transition, Fermions, Superconductivity, Systems, Lattice |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Electronic-structure calculations, Quantum impurity models, Monte-carlo, Infinite dimensions, Anderson model, Mott transition, Fermions, Superconductivity, Systems, Lattice |
| DBID source: | WOS-000293890100008 |
| DOI: | 10.1088/1367-2630/13/7/075013 |
| Nebis system number: | 001997538 |
Suppression of the critical temperature for superfluidity near the Mott transition
,
Trotzky, S., Pollet, L., Gerbier, F., Schnorrberger, U., Bloch, I., Prokof'ev, N.V., Svistunov, B., Troyer, M.,
2010
>>
| Author(s): | Trotzky, S., Pollet, L., Gerbier, F., Schnorrberger, U., Bloch, I., Prokof'ev, N.V., Svistunov, B., Troyer, M. |
| Title: | Suppression of the critical temperature for superfluidity near the Mott transition |
| Abstract: | Ultracold atomic gases in optical lattices have proven to be a controllable, tunable and clean implementation of strongly interacting quantum many-body systems. An essential prospect for such quantum simulators is their ability to map out the phase diagram of fundamental many-body model Hamiltonians. However, the results need to be validated first for representative benchmark problems through state-of-the-art numerical methods of quantum many-body theory. Here we present the first ab initio comparison between experiments and quantum Monte Carlo simulations for strongly interacting Bose gases on a lattice for large systems (up to N congruent to 3 x 10(5) particles). The comparison enables thermometry for the interacting quantum gas and to experimentally determine the finite-temperature phase diagram for bosonic superfluids in an optical lattice, revealing a suppression of the critical temperature as the transition to the Mott insulator is approached. |
| Published in: | Nature physics |
| Volume: | 6 |
| Issue: | 12 |
| Pages: | 998 - 1004 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | London, UK |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000284832600023 |
| DOI: | 10.1038/NPHYS1799 |
| Nebis system number: | 005054127 |
Subband engineering even-denominator quantum Hall states
,
Scarola, V.W., May, C., Peterson, M.R., Troyer, M.,
2010
>>
| Author(s): | Scarola, V.W., May, C., Peterson, M.R., Troyer, M. |
| Title: | Subband engineering even-denominator quantum Hall states |
| Abstract: | Proposed even-denominator fractional quantum Hall effect (FQHE) states suggest the possibility of excitations with non-Abelian braid statistics. Recent experiments on wide square quantum wells indicate even-denominator FQHE even under electrostatic tilt. We theoretically analyze these structures and develop a procedure to accurately test proposed quantum Hall wave functions. We find that tilted wells favor partial subband polarization to yield Abelian even-denominator states. Our results show that tilting quantum wells effectively engineers different interaction potentials allowing exploration of a wide variety of even-denominator states. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 82 |
| Issue: | 12 |
| Pages: | 121304 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, N.Y. |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000281658500003 |
| DOI: | 10.1103/PhysRevB.82.121304 |
| Nebis system number: | 001888782 |
Supersolid Phase with Cold Polar Molecules on a Triangular Lattice
,
Pollet, L., Picon, J. D., Buechler, H. P., Troyer, M.,
2010
>>
| Author(s): | Pollet, L., Picon, J. D., Buechler, H. P., Troyer, M. |
| Title: | Supersolid Phase with Cold Polar Molecules on a Triangular Lattice |
| Abstract: | We study a system of heteronuclear molecules on a triangular lattice and analyze the potential of this system for the experimental realization of a supersolid phase. The ground state phase diagram contains superfluid, solid, and supersolid phases. At finite temperatures and strong interactions there is an additional emulsion region, in contrast with similar models with short-range interactions. We derive the maximal critical temperature Tc and the corresponding entropy S/N=0.04(1) for supersolidity and find feasible experimental conditions for its realization. |
| Published in: | Physical review letters |
| Volume: | 104 |
| Issue: | 12 |
| Pages: | 125302 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000276072400026, PP-55151 |
| DOI: | 10.1103/PhysRevLett.104.125302 |
| Nebis system number: | 000003868 |
Itinerant Ferromagnetism of a Repulsive Atomic Fermi Gas
,
Pilati, S., Bertaina, G., Giorgini, S., Troyer, M.,
2010
>>
| Author(s): | Pilati, S., Bertaina, G., Giorgini, S., Troyer, M. |
| Title: | Itinerant Ferromagnetism of a Repulsive Atomic Fermi Gas |
| Subtitle: | A Quantum Monte Carlo Study |
| Abstract: | We investigate the phase diagram of a two-component repulsive Fermi gas at T = 0 by means of quantum Monte Carlo simulations. Both purely repulsive and resonant attractive model potentials are considered in order to analyze the limits of the universal regime where the details of interatomic forces can be neglected. The equation of state of both balanced and unbalanced systems is calculated as a function of the interaction strength and the critical density for the onset of ferromagnetism is determined. The energy of the strongly polarized gas is calculated and parametrized in terms of the physical properties of repulsive polarons, which are relevant for the stability of the fully ferromagnetic state. Finally, we analyze the phase diagram in the interaction-polarization plane under the assumption that only phases with homogeneous magnetization can be produced. |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 3 |
| Pages: | 030405 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000280008900001 |
| DOI: | 10.1103/PhysRevLett.105.030405 |
| Nebis system number: | 000003868 |
Simulation of anyons with tensor network algorithms
,
Pfeifer, R.N.C, Corboz, P., Buerschaper, O., Aguado, M., Troyer, M., Vidal, G.,
2010
>>
| Author(s): | Pfeifer, R.N.C, Corboz, P., Buerschaper, O., Aguado, M., Troyer, M., Vidal, G. |
| Title: | Simulation of anyons with tensor network algorithms |
| Abstract: | Interacting systems of anyons pose a unique challenge to condensed-matter simulations due to their non-trivial exchange statistics. These systems are of great interest as they have the potential for robust universal quantum computation but numerical tools for studying them are as yet limited. We show how existing tensor network algorithms may be adapted for use with systems of anyons and demonstrate this process for the one-dimensional multiscale entanglement renormalization ansatz (MERA). We apply the MERA to infinite chains of interacting Fibonacci anyons, computing their scaling dimensions and local scaling operators. The scaling dimensions obtained are seen to be in agreement with conformal field theory. The techniques developed are applicable to any tensor network algorithm, and the ability to adapt these ansatze for use on anyonic systems opens the door for numerical simulation of large systems of free and interacting anyons in one and two dimensions. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 82 |
| Issue: | 11 |
| Pages: | 115126 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000282270000004 |
| DOI: | 10.1103/PhysRevB.82.115126 |
| Nebis system number: | 001888782 |
Complete-graph tensor network states
,
Marti, Konrad H., Bauer, Bela, Reiher, Markus, Troyer, Matthias, Verstraete, Frank,
2010
>>
| Author(s): | Marti, Konrad H., Bauer, Bela, Reiher, Markus, Troyer, Matthias, Verstraete, Frank |
| Title: | Complete-graph tensor network states |
| Subtitle: | A new fermionic wave function ansatz for molecules |
| Abstract: | We present a class of tensor network states specifically designed to capture the electron correlation within a molecule of arbitrary structure. In this ansatz, the electronic wave function is represented by a complete-graph tensor network (CGTN) ansatz, which implements an efficient reduction of the number of variational parameters by breaking down the complexity of the high-dimensional coefficient tensor of a full-configuration-interaction (FCI) wave function. This ansatz applied to molecules is new and based on a tensor network wave function recently studied in lattice problems. We demonstrate that CGTN states approximate ground states of molecules accurately by comparison of the CGTN and FCI expansion coefficients. The CGTN parametrization is not biased towards any reference configuration, in contrast to many standard quantum chemical methods. This feature allows one to obtain accurate relative energies between CGTN states, which is central to molecular physics and chemistry. We discuss the implications for quantum chemistry and focus on the spin-state problem. Our CGTN approach is applied to the energy splitting of states of different spins for methylene and the strongly correlated ozone molecule at a transition state structure. The parameters of the tensor network ansatz are variationally optimized by means of a parallel-tempering Monte Carlo algorithm. |
| Published in: | New journal of physics |
| Volume: | 12 |
| Pages: | 103008 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000284766800008 |
| DOI: | 10.1088/1367-2630/12/10/103008 |
| Nebis system number: | 001997538 |
Measuring the equation of state of trapped ultracold bosonic systems in an optical lattice with in situ density imaging
,
Ma, Ping Nang, Pollet, Lode, Troyer, Matthias,
2010
>>
| Author(s): | Ma, Ping Nang, Pollet, Lode, Troyer, Matthias |
| Title: | Measuring the equation of state of trapped ultracold bosonic systems in an optical lattice with in situ density imaging |
| Abstract: | We analyze quantitatively how imaging techniques with single-site resolution allow to measure thermodynamical properties that cannot be inferred from time-of-flight images for the trapped Bose-Hubbard model. If the normal state extends over a sufficiently large range, the chemical potential and the temperature can be extracted from a single shot, provided the sample is in thermodynamic equilibrium. When the normal state is too narrow, temperature is low but can still be extracted using the fluctuation-dissipation theorem over the entire trap range as long as the local-density approximation remains valid, as was recently suggested by Q. Zhou and T.-L. Ho [arXiv:0908.3015]. However, for typical present-day experiments, the number of samples needed is on the order of 1000 in order to get the temperature at least 10% accurate, but it is possible to reduce the variance by 2 orders of magnitude if the density-density correlation length is short, which is the case for the Bose-Hubbard model. Our results provide further evidence that cold gases in optical lattices can be viewed as quantum analog computers. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 82 |
| Issue: | 3 |
| Pages: | 033627 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000282313000015 |
| DOI: | 10.1103/PhysRevA.82.033627 |
| Nebis system number: | 000619853 |
Diagrammatic Monte Carlo for correlated fermions
,
Kozik, Evgeny, Van Houcke, Kris, Gull, Emanuel, Pollet, Lode, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias,
2010
>>
| Author(s): | Kozik, Evgeny, Van Houcke, Kris, Gull, Emanuel, Pollet, Lode, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias |
| Title: | Diagrammatic Monte Carlo for correlated fermions |
| Abstract: | We show that Monte Carlo sampling of the Feynman diagrammatic series (DiagMC) can be used for tackling hard fermionic quantum many-body problems in the thermodynamic limit by presenting accurate results for the repulsive Hubbard model in the correlated Fermi liquid regime. Sampling Feynman's diagrammatic series for the single-particle self-energy, we can study moderate values of the on-site repulsion (U/t~4) and temperatures down to T/t=1/40. We compare our results with high-temperature series expansions and with single-site and cluster dynamical mean-field theory. |
| Published in: | EPL |
| Volume: | 90 |
| Issue: | 1 |
| Pages: | 10004 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Bristol, UK |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000279118900004 |
| DOI: | 10.1209/0295-5075/90/10004 |
| Nebis system number: | 000033031 |
Bridging Workflow and Data Provenance Using Strong Links
,
Koop, David, Santos, Emanuele, Bauer, Bela, Troyer, Matthias, Freire, Juliana, Silva, Cláudio T.,
2010
>>
| Author(s): | Koop, David, Santos, Emanuele, Bauer, Bela, Troyer, Matthias, Freire, Juliana, Silva, Cláudio T. |
| Title: | Bridging Workflow and Data Provenance Using Strong Links |
| Abstract: | As scientists continue to migrate their work to computational methods, it is important to track not only the steps involved in the computation but also the data consumed and produced. While this provenance information can be captured, in existing approaches, it often contains only weak references between data and provenance. When data files or provenance are moved or modified, it can be difficult to find the data associated with the provenance or to find the provenance associated with the data. We propose a persistent storage mechanism that manages input, intermediate, and output data files, strengthening the links between provenance and data. This mechanism provides better support for reproducibility because it ensures the data referenced in provenance information can be readily located. Another important benefit of such management is that it allows caching of intermediate data which can then be shared with other users. We present an implemented infrastructure for managing data in a provenance-aware manner and demonstrate its application in scientific projects. |
| Book title: | Scientific and statistical database management : 22nd international conference : proceedings |
| Published in: | Lecture notes in computer science |
| Volume: | 6187 |
| Pages: | 397 - 415 |
| ISBN: | 978-3-642-13817-1, 978-3-642-13818-8 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Informationssysteme|Information Systems |
| Event name: | 22nd International Working Conference on Scientific and Statistical Database Management (SSDBM 2010) |
| Event date: | June 30 - July 2, 2010 |
| Place: | Heidelberg, Germany |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295384979 |
| DOI: | 10.1007/978-3-642-13818-8_28 |
| Nebis system number: | 006130999 |
Quantitative Determination of Temperature in the Approach to Magnetic Order of Ultracold Fermions in an Optical Lattice
,
Jördens, R., Tarruell, L., Greif, D., Uehlinger, T., Strohmaier, N., Moritz, H., Esslinger, T., De Leo, L., Kollath, C., Georges, A., Scarola, V., Pollet, L., Burovski, E., Kozik, E., Troyer, M.,
2010
>>
| Author(s): | Jördens, R., Tarruell, L., Greif, D., Uehlinger, T., Strohmaier, N., Moritz, H., Esslinger, T., De Leo, L., Kollath, C., Georges, A., Scarola, V., Pollet, L., Burovski, E., Kozik, E., Troyer, M. |
| Title: | Quantitative Determination of Temperature in the Approach to Magnetic Order of Ultracold Fermions in an Optical Lattice |
| Abstract: | We perform a quantitative simulation of the repulsive Fermi-Hubbard model using an ultracold gas trapped in an optical lattice. The entropy of the system is determined by comparing accurate measurements of the equilibrium double occupancy with theoretical calculations over a wide range of parameters. We demonstrate the applicability of both high-temperature series and dynamical mean-field theory to obtain quantitative agreement with the experimental data. The reliability of the entropy determination is confirmed by a comprehensive analysis of all systematic errors. In the center of the Mott insulating cloud we obtain an entropy per atom as low as 0.77kB which is about twice as large as the entropy at the Néel transition. The corresponding temperature depends on the atom number and for small fillings reaches values on the order of the tunneling energy. |
| Published in: | Physical review letters |
| Volume: | 104 |
| Issue: | 18 |
| Pages: | 180401 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1289213129, PP-53344 |
| DOI: | 10.1103/PhysRevLett.104.180401 |
| Nebis system number: | 000003868 |
Continuous-time quantum impurity solvers
,
Gull, Emmanuel, Werner, Philipp, Millis, Andrew, Troyer, Matthias,
2010
>>
| Author(s): | Gull, Emmanuel, Werner, Philipp, Millis, Andrew, Troyer, Matthias |
| Title: | Continuous-time quantum impurity solvers |
| Abstract: | We present a brief overview of two continuous–time quantum Monte Carlo impurity solvers–a diagrammatic expansion of the partition function in the interaction and in the impurity-bath hybridization and mention a recently developed continuous-time auxiliary field method. We show that continuous-time methods deliver substantial gains in computational effeciency over previous QMC discrete-time algorithms. |
| Published in: | Physics procedia |
| Volume: | 6 |
| Pages: | 31 - 34 |
| ISSN: | 1875-3892 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Event name: | 21st Workshop of Computer Simulations Studies in Condensed Matter Physics |
| Place: | Athens, GA, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295451014 |
| DOI: | 10.1016/j.phpro.2010.09.025 |
Continuous-time quantum Monte Carlo impurity solvers
,
Gull, Emanuel, Werner, Philipp, Fuchs, Sebastian, Surer, Brigitte, Pruschke, Thomas, Troyer, Matthias,
2010
>>
| Author(s): | Gull, Emanuel, Werner, Philipp, Fuchs, Sebastian, Surer, Brigitte, Pruschke, Thomas, Troyer, Matthias |
| Title: | Continuous-time quantum Monte Carlo impurity solvers |
| Abstract: | Continuous-time quantum Monte Carlo impurity solvers are algorithms that sample the partition function of an impurity model using diagrammatic Monte Carlo techniques. The present paper describes codes that implement the interaction expansion algorithm originally developed by Rubtsov, Savkin, and Lichtenstein, as well as the hybridization expansion method developed by Werner, Millis, Troyer, et al. These impurity solvers are part of the ALPS-DMFT application package and are accompanied by an implementation of dynamical mean-field self-consistency equations for (single orbital single site) dynamical mean-field problems with arbitrary densities of states. Program summary Program title: dmft Catalogue identifier: AEIL_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEIL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: ALPS LIBRARY LICENSE version 1.1 No. of lines in distributed program, including test data, etc.: 899 806 No. of bytes in distributed program, including test data, etc.: 32 153 916 Distribution format: tar.gz Programming language: C++ Operating system: The ALPS libraries have been tested on the following platforms and compilers: Linux with GNU Compiler Collection (g++ version 3.1 and higher), and Intel C++ Compiler (icc version 7.0 and higher) MacOS X with GNU Compiler (g++ Apple-version 3.1, 3.3 and 4.0) IBM AIX with Visual Age C++ (xIC version 6.0) and GNU (g++ version 3.1 and higher) compilers Compaq Tru64 UNIX with Compq C++ Compiler (cxx) SGI IRIX with MIPSpro C++ Compiler (CC) HP-UX with HP C++ Compiler (aCC) Windows with Cygwin or coLinux platforms and GNU Compiler Collection (g++ version 3.1 and higher) RAM: 10 MB-1 GB Classification: 7.3 External routines: ALPS [1], BLAS/LAPACK, HDF5 Nature of problem: (See 121.) Quantum impurity models describe an atom or molecule embedded in a host material with which it can exchange electrons. They are basic to nanoscience as representations of quantum dots and molecular conductors and play an increasingly important role in the theory of "correlated electron" materials as auxiliary problems whose solution gives the "dynamical mean field" approximation to the self-energy and local correlation functions. Solution method: Quantum impurity models require a method of solution which provides access to both high and low energy scales and is effective for wide classes of physically realistic models. The continuous-time quantum Monte Carlo algorithms for which we present implementations here meet this challenge. Continuous-time quantum impurity methods are based on partition function expansions of quantum impurity models that are stochastically sampled to all orders using diagrammatic quantum Monte Carlo techniques. For a review of quantum impurity models and their applications and of continuous-time quantum Monte Carlo methods for impurity models we refer the reader to [2]. Additional comments: Use of dmft requires citation of this paper. Use of any ALPS program requires citation of the ALPS [1] paper. Running time: 60 s-8 h per iteration. |
| Published in: | Computer physics communications |
| Volume: | 182 |
| Issue: | 4 |
| Pages: | 1078 - 1082 |
| ISSN: | 0010-4655, 1879-2944 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Informatik allgemein|Computer Science, General, Impurity problems, Impurity solvers, DMFT, CT-QMC, CT-HYB, CT-INT |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Impurity problems, Impurity solvers, DMFT, CT-QMC, CT-HYB, CT-INT |
| DBID source: | FORM-1295173158, WOS-000288404300021 |
| DOI: | 10.1016/j.cpc.2010.12.050 |
| Nebis system number: | 000045256 |
Comment on “Exact Bosonization for an Interacting Fermi Gas in Arbitrary Dimensions”
,
Galanakis, D., Yang, S., Assaad, F.F., Jarrell, M., Werner, Philipp, Troyer, Matthias,
2010
>>
| Author(s): | Galanakis, D., Yang, S., Assaad, F.F., Jarrell, M., Werner, Philipp, Troyer, Matthias |
| Title: | Comment on “Exact Bosonization for an Interacting Fermi Gas in Arbitrary Dimensions” |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 15 |
| Pages: | 159701 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000282511800023, PP-55149 |
| DOI: | 10.1103/PhysRevLett.105.159701 |
| Nebis system number: | 000003868 |
Thermodynamics of the 3D Hubbard model on approach to the Neel transition
,
Fuchs, Sebastian, Gull, Emanuel, Pollet, Lode, Burovski, Evgeni, Kozik, Evgeny, Pruschke, Thomas, Troyer, Matthias,
2010
>>
| Author(s): | Fuchs, Sebastian, Gull, Emanuel, Pollet, Lode, Burovski, Evgeni, Kozik, Evgeny, Pruschke, Thomas, Troyer, Matthias |
| Title: | Thermodynamics of the 3D Hubbard model on approach to the Neel transition |
| Abstract: | We study the thermodynamic properties of the 3D Hubbard model for temperatures down to the Neel temperature by using cluster dynamical mean-field theory. In particular, we calculate the energy, entropy, density, double occupancy, and nearest-neighbor spin correlations as a function of chemical potential, temperature, and repulsion strength. To make contact with cold-gas experiments, we also compute properties of the system subject to an external trap in the local density approximation. We find that an entropy per particle S/N approximate to 0.65(6) at U/t = 8 is sufficient to achieve a Neel state in the center of the trap, substantially higher than the entropy required in a homogeneous system. Precursors to antiferromagnetism can clearly be observed in nearest-neighbor spin correlators. |
| Published in: | Physical review letters |
| Volume: | 10 |
| Issue: | 3 |
| Pages: | 030401 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York, NY |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294964836, WOS-000286742200001 |
| DOI: | 10.1103/PhysRevLett.106.030401 |
| Nebis system number: | 000003868 |
The Beliaev technique for a weakly interacting Bose gas
,
Cappogrosso-Sansone, B., Giorgini, S., Pilati, S., Pollet, L., Prokof'ev, N., Svistunov, B., Troyer, M.,
2010
>>
| Author(s): | Cappogrosso-Sansone, B., Giorgini, S., Pilati, S., Pollet, L., Prokof'ev, N., Svistunov, B., Troyer, M. |
| Title: | The Beliaev technique for a weakly interacting Bose gas |
| Abstract: | Aiming at simplicity of explicit equations and, at the same time, controllable accuracy of the theory, we present our results for all the thermodynamic quantities and correlation functions for a weakly interacting Bose gas at short-to-intermediate distances obtained within an improved version of Beliaev's diagrammatic technique. With a controllably small (but essentially finite) Bogoliubov's symmetry-breaking term, Beliaev's diagrammatic technique becomes regular in the infrared limit. Up to higher-order terms (for which we present parametric order-of-magnitude estimates), the partition function and entropy of the system formally correspond to those of a non-interacting bosonic (pseudo-)Hamiltonian with a temperature-dependent Bogoliubov-type dispersion relation. Away from the fluctuation region, this approach provides the most accurate—in fact, the best possible within the Bogoliubov-type pseudo-Hamiltonian framework—description of the system with controlled accuracy. It produces accurate answers for the off-diagonal correlation functions up to distances where the behavior of correlators is controlled by generic hydrodynamic relations and, thus, can be accurately extrapolated to arbitrarily large scales. In the fluctuation region, the non-perturbative contributions are given by universal (for all weakly interacting U(1) systems) constants and scaling functions, which can be obtained separately—by simulating classical U(1) models—and then used to extend the description of the weakly interacting Bose gas to the fluctuation region. The technique works in all spatial dimensions, and we explicitly checked the validity of this technique against first-principle Monte Carlo simulations for various thermodynamic properties and the single-particle density matrix. |
| Published in: | New journal of physics |
| Volume: | 12 |
| Issue: | 4 |
| Pages: | 043010 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294358575 |
| DOI: | 10.1088/1367-2630/12/4/043010 |
| Nebis system number: | 001997538 |
Optimized broad-histogram simulations for strong first-order phase transitions
,
Bauer, Bela, Gull, Emanuel, Trebst, Simon, Troyer, Matthias, Huse, David A.,
2010
>>
| Author(s): | Bauer, Bela, Gull, Emanuel, Trebst, Simon, Troyer, Matthias, Huse, David A. |
| Title: | Optimized broad-histogram simulations for strong first-order phase transitions |
| Subtitle: | Droplet transitions in the large-Q Potts model |
| Abstract: | The numerical simulation of strongly first-order phase transitions has remained a notoriously difficult problem even for classical systems due to the exponentially suppressed (thermal) equilibration in the vicinity of such a transition. In the absence of efficient update techniques, a common approach for improving equilibration in Monte Carlo simulations is broadening the sampled statistical ensemble beyond the bimodal distribution of the canonical ensemble. Here we show how a recently developed feedback algorithm can systematically optimize such broad-histogram ensembles and significantly speed up equilibration in comparison with other extended ensemble techniques such as flat-histogram, multicanonical and Wang-Landau sampling. We simulate, as a prototypical example of a strong first-order transition, the two-dimensional Potts model with up to Q = 250 different states in large systems. The optimized histogram develops a distinct multi-peak structure, thereby resolving entropic barriers and their associated phase transitions in the phase coexistence region-such as droplet nucleation and annihilation, and droplet-strip transitions for systems with periodic boundary conditions. We characterize the efficiency of the optimized histogram sampling by measuring round-trip times tau(N, Q) across the phase transition for samples comprised of N spins. While we find power-law scaling of tau versus N for small Q less than or similar to 50 and N less than or similar to 40(2), we observe a crossover to exponential scaling for larger Q. These results demonstrate that despite the ensemble optimization, broad-histogram simulations cannot fully eliminate the supercritical slowing down at strongly first-order transitions. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2010 |
| Issue: | 1 |
| Pages: | P01020 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | classical Monte Carlo simulations, classical phase transitions (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | classical Monte Carlo simulations, classical phase transitions (theory) |
| DBID source: | WOS-000274266600004 |
| DOI: | 10.1088/1742-5468/2010/01/P01020 |
| Nebis system number: | 004699119 |
Distinguishing phases with ansatz wave functions
,
Bauer, B., Troyer, M., Scarola, V. W., Whaley, K. B.,
2010
>>
| Author(s): | Bauer, B., Troyer, M., Scarola, V. W., Whaley, K. B. |
| Title: | Distinguishing phases with ansatz wave functions |
| Abstract: | We propose an indistinguishability measure for assessment of ansatz wave functions with numerically determined wave functions. The measure efficiently compares all correlation functions of two states and can therefore be used to distinguish phases by defining correlator classes for ansatz wave functions. It also allows identification of quantum critical points. We demonstrate the approach for the transverse Ising and bilinear-biquadratic Heisenberg models, using the matrix-product state formalism with the time-evolving block decimation algorithm. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 81 |
| Issue: | 8 |
| Pages: | 085118 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000275053300045 |
| DOI: | 10.1103/PhysRevB.81.085118 |
| Nebis system number: | 001888782 |
Dynamical Mean Field Solution of the Bose-Hubbard Model
,
Anders, Peter, Gull, Emanuel, Pollet, Lode, Troyer, Matthias, Werner, Philipp,
2010
>>
| Author(s): | Anders, Peter, Gull, Emanuel, Pollet, Lode, Troyer, Matthias, Werner, Philipp |
| Title: | Dynamical Mean Field Solution of the Bose-Hubbard Model |
| Abstract: | We present the effective action and self-consistency equations for the bosonic dynamical mean field approximation to the bosonic Hubbard model and show that it provides remarkably accurate phase diagrams and correlation functions. To solve the bosonic dynamical mean field equations, we use a continuous-time Monte Carlo method for bosonic impurity models based on a diagrammatic expansion in the hybridization and condensate coupling. This method is readily generalized to bosonic mixtures, spinful bosons, and Bose-Fermi mixtures. |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 9 |
| Pages: | 096402 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York, NY, USA |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000281164200013 |
| DOI: | 10.1103/PhysRevLett.105.096402 |
| Nebis system number: | 000003868 |
Estimating errors reliably in Monte Carlo simulations of the Ehrenfest model
,
Ambegaokar, Vinay, Troyer, Matthias,
2010
>>
| Author(s): | Ambegaokar, Vinay, Troyer, Matthias |
| Title: | Estimating errors reliably in Monte Carlo simulations of the Ehrenfest model |
| Abstract: | We use the Ehrenfest urn model to illustrate the subtleties of error estimation in Monte Carlo simulations. We discuss how the smooth results of correlated sampling in Markov chains can fool one's perception of the accuracy of the data and show via numerical and analytical methods how to obtain reliable error estimates from correlated samples. |
| Published in: | American journal of physics |
| Volume: | 78 |
| Issue: | 2 |
| Pages: | 150 - 157 |
| ISSN: | 0002-9505 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | College Park |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000273597200005, PP-55154 |
| DOI: | 10.1119/1.3247985 |
| Nebis system number: | 000042056 |
Thermal Canting of Spin-Bond Order
,
Scarola, V. W., Whaley, K. B., Troyer, M.,
2009
>>
| Author(s): | Scarola, V. W., Whaley, K. B., Troyer, M. |
| Title: | Thermal Canting of Spin-Bond Order |
| Abstract: | Magnetism arising from coupled spin and spatial degrees of freedom underlies the properties of a broad array of physical systems. We study here the interplay between correlations in spin and space for the quantum compass model in a finite external field, using quantum Monte Carlo methods. We find that finite temperatures cant the spin and space (bond) correlations, with increasing temperature, even reorienting spin correlations between orthogonal spatial directions. We develop a coupled mean-field theory to understand this effect in terms of the underlying quantum critical properties of crossed Ising chains in transverse fields and an effective field that weakens upon increasing temperature. Thermal canting offers an experimental signature of spin-bond anisotropy. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 79 |
| Issue: | 8 |
| Pages: | 085113-1 - 085113-5 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Ising model, magnetic anisotropy, Monte Carlo methods, spin dynamics, thermal analysis |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Ising model, magnetic anisotropy, Monte Carlo methods, spin dynamics, thermal analysis |
| DBID source: | PP-44078 |
| DOI: | 10.1103/PhysRevB.79.085113 |
| Nebis system number: | 001888782 |
Absence of a Direct Superfluid to Mott Insulator Transition in Disordered Bose Systems
,
Pollet, L., Prokof'ev, N.V., Svistunov, B.V., Troyer, M.,
2009
>>
| Author(s): | Pollet, L., Prokof'ev, N.V., Svistunov, B.V., Troyer, M. |
| Title: | Absence of a Direct Superfluid to Mott Insulator Transition in Disordered Bose Systems |
| Abstract: | We prove the absence of a direct quantum phase transition between a superfluid and a Mott insulator in a bosonic system with generic, bounded disorder. We also prove the compressibility of the system on the superfluid–insulator critical line and in its neighborhood. These conclusions follow from a general theorem of inclusions, which states that for any transition in a disordered system, one can always find rare regions of the competing phase on either side of the transition line. Quantum Monte Carlo simulations for the disordered Bose-Hubbard model show an even stronger result, important for the nature of the Mott insulator to Bose glass phase transition: the critical disorder bound Δc corresponding to the onset of disorder-induced superfluidity, satisfies the relation Δc>Eg/2, with Eg/2 the half-width of the Mott gap in the pure system. |
| Published in: | Physical review letters |
| Volume: | 103 |
| Issue: | 14 |
| Pages: | 140402 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-55153 |
| DOI: | 10.1103/PhysRevLett.103.140402 |
| Nebis system number: | 000003868 |
Phase diagram of the disordered Bose-Hubbard model
,
Gurarie, V., Pollet, L., Prokof'ev, N.V., Svistunov, B.V., Troyer, M.,
2009
>>
| Author(s): | Gurarie, V., Pollet, L., Prokof'ev, N.V., Svistunov, B.V., Troyer, M. |
| Title: | Phase diagram of the disordered Bose-Hubbard model |
| Abstract: | We establish the phase diagram of the disordered three-dimensional Bose-Hubbard model at unity filling which has been controversial for many years. The theorem of inclusions, proven by Pollet et al. [Phys. Rev. Lett. 103, 140402 (2009)] states that the Bose-glass phase always intervenes between the Mott insulating and superfluid phases. Here, we note that assumptions on which the theorem is based exclude phase transitions between gapped (Mott insulator) and gapless phases (Bose glass). The apparent paradox is resolved through a unique mechanism: such transitions have to be of the Griffiths type when the vanishing of the gap at the critical point is due to a zero concentration of rare regions where extreme fluctuations of disorder mimic a regular gapless system. An exactly solvable random transverse field Ising model in one dimension is used to illustrate the point. A highly nontrivial overall shape of the phase diagram is revealed with the worm algorithm. The phase diagram features a long superfluid finger at strong disorder and on-site interaction. Moreover, bosonic superfluidity is extremely robust against disorder in a broad range of interaction parameters; it persists in random potentials nearly 50 (!) times larger than the particle half-bandwidth. Finally, we comment on the feasibility of obtaining this phase diagram in cold-atom experiments, which work with trapped systems at finite temperature. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 80 |
| Issue: | 21 |
| Pages: | 214519 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-55152 |
| DOI: | 10.1103/PhysRevB.80.214519 |
| Nebis system number: | 001888782 |
Topology-driven quantum phase transitions in time-reversal-invariant anyonic quantum liquids
,
Gils, Charlotte, Ardonne, Eddy, Trebst, Simon, Ludwig, Andreas, Troyer, Matthias, Wang, Zhenghan,
2009
>>
| Author(s): | Gils, Charlotte, Ardonne, Eddy, Trebst, Simon, Ludwig, Andreas, Troyer, Matthias, Wang, Zhenghan |
| Title: | Topology-driven quantum phase transitions in time-reversal-invariant anyonic quantum liquids |
| Abstract: | Indistinguishable particles in two dimensions can be characterized by anyonic quantum statistics, which is more general than that of bosons or fermions. Anyons emerge as quasiparticles in fractional quantum Hall states and in certain frustrated quantum magnets. Quantum liquids of anyons show degenerate ground states, where the degeneracy depends on the topology of the underlying surface. Here, we present a new type of continuous quantum phase transition in such anyonic quantum liquids, which is driven by quantum fluctuations of the topology. The critical state connecting two anyonic liquids on surfaces with different topologies is reminiscent of the notion of a 'quantum foam' with fluctuations on all length scales. This exotic quantum phase transition arises in a microscopic model of interacting anyons for which we present an exact solution in a linear geometry. We introduce an intuitive physical picture of this model that unifies string nets and loop gases, and provide a simple description of topological quantum phases and their phase transitions. |
| Published in: | Nature physics |
| Volume: | 5 |
| Issue: | 11 |
| Pages: | 834 - 839 |
| ISSN: | 1745-2473, 1745-2481 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-46625 |
| DOI: | 10.1038/nphys1396 |
| Nebis system number: | 005054127 |
ENCORE
,
Fabricio Albuquerque, A., Katzgraber, Helmut G., Troyer, Matthias,
2009
>>
| Author(s): | Fabricio Albuquerque, A., Katzgraber, Helmut G., Troyer, Matthias |
| Title: | ENCORE |
| Subtitle: | An Extended Contractor Renormalization algorithm |
| Abstract: | Contractor renormalization (CORE) is a real-space renormalization-group method to derive effective Hamiltionians for microscopic models. The original CORE method is based on a real-space decomposition of the lattice into small blocks and the effective degrees of freedom on the lattice are tensor products of those on the small blocks. We present an extension of the CORE method that overcomes this restriction. Our generalization allows the application of CORE to derive arbitrary effective models whose Hilbert space is not just a tensor product of local degrees of freedom. The method is especially well suited to search for microscopic models to emulate low-energy exotic models and can guide the design of quantum devices. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 79 |
| Issue: | 4 |
| Pages: | 046712 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Hilbert spaces, Numerical analysis, Quantum theory, Renormalisation, Tensors |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Hilbert spaces, Numerical analysis, Quantum theory, Renormalisation, Tensors |
| DBID source: | PP-44019, PP-52868 |
| DOI: | 10.1103/PhysRevE.79.046712 |
| Nebis system number: | 004109079 |
Assessing the accuracy of projected entangled-pair states on infinite lattices
,
Bauer, B., Vidal, G., Troyer, M.,
2009
>>
| Author(s): | Bauer, B., Vidal, G., Troyer, M. |
| Title: | Assessing the accuracy of projected entangled-pair states on infinite lattices |
| Abstract: | Generalizations of the density matrix renormalization group method have long been sought after. In this paper, we assess the accuracy of projected entangled-pair states on infinite lattices by comparing with quantum Monte Carlo results for several non-frustrated spin- systems. Furthermore, we apply the method to a frustrated quantum system. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2009 |
| Issue: | 09 |
| Pages: | P09006 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2009-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | spin chains, ladders and planes (theory): quantum phase transitions (theory), other numerical approaches, frustrated systems (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | spin chains, ladders and planes (theory): quantum phase transitions (theory), other numerical approaches, frustrated systems (theory) |
| DBID source: | PP-52214 |
| DOI: | 10.1088/1742-5468/2009/09/P09006 |
| Nebis system number: | 004699119 |
Spin freezing transition and non-fermi-liquid self-energy in a three-orbital model
,
Werner, Philipp, Gull, Emanuel, Troyer, Matthias, Millis, Andrew J.,
2008
>>
| Author(s): | Werner, Philipp, Gull, Emanuel, Troyer, Matthias, Millis, Andrew J. |
| Title: | Spin freezing transition and non-fermi-liquid self-energy in a three-orbital model |
| Abstract: | A single-site dynamical mean-field study of a three band model with the rotationally invariant interactions appropriate to the t2g levels of a transition metal oxide reveals a quantum phase transition between a paramagnetic metallic phase and an incoherent metallic phase with frozen moments. The Mott transitions occurring at electron densities n=2, 3 per site take place inside the frozen moment phase. The critical line separating the two phases is characterized by a self-energy with the frequency dependence Σ(ω)˜ω and a broad quantum critical regime. The findings are discussed in the context of the power law observed in the optical conductivity of SrRuO3. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 16 |
| Pages: | 166405-1 - 166405-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43109, PP-44108 |
| DOI: | 10.1103/PhysRevLett.101.166405 |
| Nebis system number: | 000003868 |
Local interactions and non-Abelian quantum loop gases
,
Troyer, Matthias, Trebst, Simon, Shtengel, Kirill, Nayak, Chetan,
2008
>>
| Author(s): | Troyer, Matthias, Trebst, Simon, Shtengel, Kirill, Nayak, Chetan |
| Title: | Local interactions and non-Abelian quantum loop gases |
| Abstract: | Two-dimensional quantum loop gases are elementary examples of topological ground states with Abelian or non-Abelian anyonic excitations. While Abelian loop gases appear as ground states of local, gapped Hamiltonians such as the toric code, we show that gapped non-Abelian loop gases require nonlocal interactions (or nontrivial inner products). Perturbing a local, gapless Hamiltonian with an anticipated “non-Abelian” ground-state wave function immediately drives the system into the Abelian phase, as can be seen by measuring the Hausdorff dimension of loops. Local quantum critical behavior is found in a loop gas in which all equal-time correlations of local operators decay exponentially. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 23 |
| Pages: | 230401-1 - 230401- |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43827 |
| DOI: | 10.1103/PhysRevLett.101.230401 |
| Nebis system number: | 000003868 |
Collective states of interacting Fibonacci anyons
,
Trebst, Simone, Ardonne, Eddy, Feiguin, Adrian, Huse, David A., Ludwig, Andreas W.W., Troyer, Matthias,
2008
>>
| Author(s): | Trebst, Simone, Ardonne, Eddy, Feiguin, Adrian, Huse, David A., Ludwig, Andreas W.W., Troyer, Matthias |
| Title: | Collective states of interacting Fibonacci anyons |
| Abstract: | We show that chains of interacting Fibonacci anyons can support a wide variety of collective ground states ranging from extended critical, gapless phases to gapped phases with ground-state degeneracy and quasiparticle excitations. In particular, we generalize the Majumdar-Ghosh Hamiltonian to anyonic degrees of freedom by extending recently studied pairwise anyonic interactions to three-anyon exchanges. The energetic competition between two- and three-anyon interactions leads to a rich phase diagram that harbors multiple critical and gapped phases. For the critical phases and their higher symmetry end points we numerically establish descriptions in terms of two-dimensional conformal field theories. A topological symmetry protects the critical phases and determines the nature of gapped phases. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 5 |
| Pages: | 050401-1 - 050401-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43824 |
| DOI: | 10.1103/PhysRevLett.101.050401 |
| Nebis system number: | 000003868 |
A Short Introduction to Fibonacci Anyon Models
,
Trebst, Simon, Troyer, Matthias, Wang, Zhenghan, Ludwig, Andreas W.W.,
2008
>>
| Author(s): | Trebst, Simon, Troyer, Matthias, Wang, Zhenghan, Ludwig, Andreas W.W. |
| Title: | A Short Introduction to Fibonacci Anyon Models |
| Abstract: | We discuss how to construct models of interacting anyons by generalizing quantum spin Hamiltonians to anyonic degrees of freedom. The simplest interactions energetically favor pairs of anyons to fuse into the trivial (“identity") channel, similar to the quantum Heisenberg model favoring pairs of spins to form spin singlets. We present an introduction to the theory of anyons and discuss in detail how basis sets and matrix representations of the interaction terms can be obtained, using non-Abelian Fibonacci anyons as example. Besides discussing the “golden chain”, a one-dimensional system of anyons with nearest neighbor interactions, we also present the derivation of more complicated interaction terms, such as three-anyon interactions in the spirit of the Majumdar-Ghosh spin chain, longer range interactions and two-leg ladders. We also discuss generalizations to anyons with general non-Abelian SU(2)k statistics. The k→∞ limit of the latter yields ordinary SU(2) spin chains. |
| Published in: | Progress of theoretical physics. Supplement |
| Volume: | 176 |
| Pages: | 384 - 407 |
| ISSN: | 0375-9687 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Kyoto |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43829 |
| DOI: | 10.1143/PTPS.176.384 |
| Nebis system number: | 000016191 |
Ensemble Optimization Techniques for the Simulation of Slowly Equilibrating Systems
,
Trebst, S., Huse, D.A., Gull, E., Katzgraber, H.G., Hansmann, U.H.E., Troyer, M.,
2008
>>
| Author(s): | Trebst, S., Huse, D.A., Gull, E., Katzgraber, H.G., Hansmann, U.H.E., Troyer, M. |
| Title: | Ensemble Optimization Techniques for the Simulation of Slowly Equilibrating Systems |
| Abstract: | Competing phases or interactions in complex many-particle systems can result in free energy barriers that strongly suppress thermal equilibration. Here we discuss how extended ensemble Monte Carlo simulations can be used to study the equilibrium behavior of such systems. Special focus will be given to a recently developed adaptive Monte Carlo technique that is capable to explore and overcome the entropic barriers which cause the slow-down. We discuss this technique in the context of broad-histogram Monte Carlo algorithms as well as its application to replica-exchange methods such as parallel tempering. We briefly discuss a number of examples including low-temperature states of magnetic systems with competing interactions and dense liquids. |
| Book title: | Computer Simulation Studies in Condensed-Matter Physics XIX |
| Published in: | Springer proceedings in physics |
| Volume: | 123 |
| Pages: | 33 - 47 |
| ISBN: | 978-3-540-85624-5, 978-3-540-85625-2 |
| ISSN: | 0930-8989 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Kondensierte Materie|Condensed Matter |
| Event name: | 19th Workshop on Recent Developments in Computer Simulation Studies in Condensed Matter Physics |
| Event date: | February 20-24, 2006 |
| Place: | Athens, GA, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26186, PP-52880 |
| DOI: | 10.1007/978-3-540-85625-2_6 |
| Nebis system number: | 005759231 |
Discerning incompressible and compressible phases of cold atoms in optical lattices
,
Scarola, V. W., Pollet, L., Oitmaa, J., Troyer, M.,
2008
>>
| Author(s): | Scarola, V. W., Pollet, L., Oitmaa, J., Troyer, M. |
| Title: | Discerning incompressible and compressible phases of cold atoms in optical lattices |
| Abstract: | Experiments with cold atoms trapped in optical lattices offer the potential to realize a variety of novel phases but suffer from severe spatial inhomogeneity that can obscure signatures of new phases of matter and phase boundaries. We use a high temperature series expansion to show that compressibility in the core of a trapped Fermi-Hubbard system is related to measurements of changes in double occupancy. This core compressibility filters out edge effects, offering a direct probe of compressibility independent of inhomogeneity. A comparison with experiments is made. |
| Published in: | Physical review letters |
| Volume: | 102 |
| Issue: | 13 |
| Pages: | 135302 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-44077 |
| DOI: | 10.1103/PhysRevLett.102.135302 |
| Nebis system number: | 000003868 |
Temperature changes when adiabatically ramping up an optical lattice
,
Pollet, Lode, Kollath, Corinna, Van Houcke, Kris, Troyer, Matthias,
2008
>>
| Author(s): | Pollet, Lode, Kollath, Corinna, Van Houcke, Kris, Troyer, Matthias |
| Title: | Temperature changes when adiabatically ramping up an optical lattice |
| Abstract: | When atoms are loaded into an optical lattice, the process of gradually turning on the lattice is almost adiabatic. In this paper, we investigate how the temperature changes when going from the gapless superfluid phase to the gapped Mott phase along isentropic lines. To do so we calculate the entropy in the single-band Bose–Hubbard model for various densities, interaction strengths and temperatures in one and two dimensions for homogeneous and trapped systems. Our theory is able to reproduce the experimentally observed visibilities and therefore strongly supports the view that current experiments remain in the quantum regime for the considered lattice depths with low temperatures and minimal heating. |
| Published in: | New journal of physics : NJP : an Institute of Physics & Deutsche Physikalische Gesellschaft journal |
| Volume: | 10 |
| Issue: | 6 |
| Pages: | 065001-1 - 065001-31 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | s.l. |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-44100 |
| DOI: | 10.1088/1367-2630/10/6/065001 |
| Nebis system number: | 001997538 |
Mixture of bosonic and spin-polarized fermionic atoms in an optical lattice
,
Pollet, Lode, Kollath, Corinna, Schollwöck, Ulrich, Troyer, Matthias,
2008
>>
| Author(s): | Pollet, Lode, Kollath, Corinna, Schollwöck, Ulrich, Troyer, Matthias |
| Title: | Mixture of bosonic and spin-polarized fermionic atoms in an optical lattice |
| Abstract: | We investigate the properties of trapped Bose-Fermi mixtures for experimentally relevant parameters in one dimension. The effect of the attractive Bose-Fermi interaction onto the bosons is to deepen the parabolic trapping potential, and to reduce the bosonic repulsion in higher order. This leads for many situations to an increase in bosonic coherence. The opposite effect was observed in 87Rb-40K experiments, most likely due to a sharp rise in temperature. We also discuss low-temperature features, such as a bosonic Mott insulator transition driven by the fermion concentration, and the formation of composite particles such as polarons and molecules. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 77 |
| Issue: | 2 |
| Pages: | 023608 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Subjects: | Bose-Einstein condensation |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Bose-Einstein condensation |
| DBID source: | PP-26273, PP-32785 |
| DOI: | 10.1103/PhysRevA.77.023608 |
| Nebis system number: | 000619853 |
Local stress and superfluid properties of solid He-4
,
Pollet, L., Boninsegni, M., Kuklov, A. B., Prokof'ev, N. V., Svistunov, B. V., Troyer, M.,
2008
>>
| Author(s): | Pollet, L., Boninsegni, M., Kuklov, A. B., Prokof'ev, N. V., Svistunov, B. V., Troyer, M. |
| Title: | Local stress and superfluid properties of solid He-4 |
| Abstract: | We provide a semiquantitative tool, derived from first-principles simulations, for answering the question of whether certain types of defects in solid He-4 support mass superflow. Although ideal crystals of He-4 are not supersolid, the gap for vacancy creation closes when applying a moderate stress. While a homogeneous system becomes unstable at this point, the stressed core of crystalline defects (dislocations and grain boundaries) can turn superfluid. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 9 |
| Pages: | 097202-1 - 097202-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43922 |
| DOI: | 10.1103/PhysRevLett.101.097202 |
| Nebis system number: | 000003868 |
Mechanisms for spin supersolidity in S=(1/2) spin-dimer antiferromagnets
,
Picon, J.-D., Albuquerque, A.F., Schmidt, K.P., Laflorencie, N., Troyer, M., Mila, F.,
2008
>>
| Author(s): | Picon, J.-D., Albuquerque, A.F., Schmidt, K.P., Laflorencie, N., Troyer, M., Mila, F. |
| Title: | Mechanisms for spin supersolidity in S=(1/2) spin-dimer antiferromagnets |
| Abstract: | Using perturbative expansions and the contractor renormalization (CORE) algorithm, we obtain effective hard-core bosonic Hamiltonians describing the low-energy physics of S=1/2 spin-dimer antiferromagnets known to display supersolid phases under an applied magnetic field. The resulting effective models are investigated by means of mean-field analysis and quantum Monte Carlo simulations. A "leapfrog mechanism," through means of which extra singlets delocalize in a checkerboard-solid environment via correlated hoppings, is unveiled that accounts for the supersolid behavior. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 78 |
| Issue: | 18 |
| Pages: | 184418-1 - 184418-11 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-47506 |
| DOI: | 10.1103/PhysRevB.78.184418 |
| Nebis system number: | 001888782 |
A classical picture of the role of vacancies and interstitials in Helium-4
,
Ma, Ping Nang, Pollet, Lode, Troyer, Matthias, Zhang, Fu Chun,
2008
>>
| Author(s): | Ma, Ping Nang, Pollet, Lode, Troyer, Matthias, Zhang, Fu Chun |
| Title: | A classical picture of the role of vacancies and interstitials in Helium-4 |
| Abstract: | Motivated by experimental hints for supersolidity in Helium-4, we perform Monte Carlo simulations of vacancies and interstitials in a classical two-and three-dimensional Lennard-Jones solid. We confirm a strong binding energy of vacancies which is of the order of the Lennard-Jones attraction. This is reminiscent of what has been found for vacancies in Quantum Monte Carlo simulations. In addition, we find a strong attraction and large binding energy of interstitials in two-dimensional simulations. This is mainly due to the formation of a pair of dislocations by clustering interstitials, which minimizes the elastic deformation energy. We interpret the results in light of the properties of Helium-4. |
| Published in: | Journal of low temperature physics |
| Volume: | 152 |
| Issue: | 5-6 |
| Pages: | 156 - 163 |
| ISSN: | 0022-2291, 1573-7357 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Helium, Lennard Jones, Vacancies, Interstitials, Phase separation, Monte Carlo, Binding |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Helium, Lennard Jones, Vacancies, Interstitials, Phase separation, Monte Carlo, Binding |
| DBID source: | PP-34827, PP-44099 |
| DOI: | 10.1007/s10909-008-9816-4 |
| Nebis system number: | 000049402 |
Influence of the trap shape on the detection of the superfluid
,
Ma, Ping N., Yang, Kai Y., Pollet, Lode, Porto, J. V., Troyer, Matthias, Zhang, Fu C.,
2008
>>
| Author(s): | Ma, Ping N., Yang, Kai Y., Pollet, Lode, Porto, J. V., Troyer, Matthias, Zhang, Fu C. |
| Title: | Influence of the trap shape on the detection of the superfluid |
| Subtitle: | Mott-insulator transition |
| Abstract: | The coexistence of superfluid and Mott insulator, due to the quadratic confinement potential in current optical lattice experiments, makes the accurate detection of the superfluid-Mott-insulator transition difficult. Studying alternative trapping potentials which are experimentally realizable and have a flatter center, we find that the transition can be better resolved, but at the cost of a more difficult tuning of the particle filling. When mapping out the phase diagram using local probes and the local density approximation we find that the smoother gradient of the parabolic trap is advantageous. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 78 |
| Issue: | 2 |
| Pages: | 023605-1 - 023605-5 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Subjects: | Bose-Einstein condensation, metal-insulator transition, optical lattices, phase diagrams, quantum optics |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Bose-Einstein condensation, metal-insulator transition, optical lattices, phase diagrams, quantum optics |
| DBID source: | PP-43927 |
| DOI: | 10.1103/PhysRevA.78.023605 |
| Nebis system number: | 000619853 |
Deconfined Criticality
,
Kuklov, A. B., Matsumoto, M., Prokof'ev, N. V., Svistunov, B. V., Troyer, M.,
2008
>>
| Author(s): | Kuklov, A. B., Matsumoto, M., Prokof'ev, N. V., Svistunov, B. V., Troyer, M. |
| Title: | Deconfined Criticality |
| Subtitle: | Generic First-Order Transition in the SU(2) Symmetry Case |
| Abstract: | Monte Carlo simulations of the SU(2)-symmetric deconfined critical point action reveal strong violations of scale invariance for the deconfinement transition. We find compelling evidence that the generic runaway renormalization flow of the gauge coupling is to a weak first-order transition, similar to the case of U(1)×U(1) symmetry. Our results imply that recent numeric studies of the Nèel antiferromagnet to valence bond solid quantum phase transition in SU(2)-symmetric models were not accurate enough in determining the nature of the transition. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 5 |
| Pages: | 050405-1 - 050405-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Unknown |
| DBID source: | PP-43825 |
| DOI: | 10.1103/PhysRevLett.101.050405 |
| Nebis system number: | 000003868 |
Local order and the gapped phase of the Hubbard model
,
Gull, Emanuel, Werner, Philipp, Wang, X., Troyer, Matthias, Millis, A. J.,
2008
>>
| Author(s): | Gull, Emanuel, Werner, Philipp, Wang, X., Troyer, Matthias, Millis, A. J. |
| Title: | Local order and the gapped phase of the Hubbard model |
| Subtitle: | A plaquette dynamical mean-field investigation |
| Abstract: | The four-site "DCA" method of including intersite correlations in the dynamical mean-field theory is used to investigate the metal-insulator transition in the Hubbard model. At half-filling a gap-opening transition is found to occur as the interaction strength is increased beyond a critical value. The gapped behavior found in the 4-site DCA approximation is shown to be associated with the onset of strong antiferromagnetic and singlet correlations and the transition is found to be potential energy driven. It is thus more accurately described as a Slater phenomenon ( induced by strong short-range order) than as a Mott phenomenon. Doping the gapped phase leads to a non-Fermi-liquid state with a Fermi surface only in the nodal regions and a pseudogap in the antinodal regions at lower dopings x less than or similar to 0.15 and to a Fermi-liquid phase at higher dopings. |
| Published in: | EPL |
| Volume: | 84 |
| Issue: | 3 |
| Pages: | 37009 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43108, PP-44106 |
| DOI: | 10.1209/0295-5075/84/37009 |
| Nebis system number: | 000033031 |
Continuous-time auxiliary field Monte Carlo for quantum impurity models
,
Gull, Emanuel, Werner, Philipp, Parcollet, Olivier, Troyer, Matthias,
2008
>>
| Author(s): | Gull, Emanuel, Werner, Philipp, Parcollet, Olivier, Troyer, Matthias |
| Title: | Continuous-time auxiliary field Monte Carlo for quantum impurity models |
| Abstract: | We present a continuous-time Monte Carlo method for quantum impurity models, which combines a weak-coupling expansion with an auxiliary-field decomposition. The method is considerably more efficient than Hirsch-Fye and free of time discretization errors, and is particularly useful as impurity solver in large cluster dynamical mean-field theory (DMFT) calculations. |
| Published in: | EPL : a letters journal exploring the frontiers of physics |
| Volume: | 82 |
| Issue: | 5 |
| Pages: | 57003 - 57003 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-44111 |
| DOI: | 10.1209/0295-5075/82/57003 |
| Nebis system number: | 000033031 |
Quantum Monte Carlo study of a two-species bosonic Hubbard model
,
Guertler, Siegfried, Troyer, Matthias, Zhang, Fu-Chun,
2008
>>
| Author(s): | Guertler, Siegfried, Troyer, Matthias, Zhang, Fu-Chun |
| Title: | Quantum Monte Carlo study of a two-species bosonic Hubbard model |
| Abstract: | We consider a two-species hard-core boson Hubbard model for a supersolid, where two types of bosons represent vacancies and interstitials doped into a commensurate crystal. The on-site interspecies interaction can create bound states of vacancies and interstitials facilitating vacancy condensation at lower energies than in a single-species model, as suggested in an earlier mean-field study. Here, we carry out quantum Monte Carlo simulations to study possible supersolid phases of the model, which correspond to superfluid phases of the vacancies or interstitials. At low temperatures, we find three distinct superfluid phases. The extent of the phases and the nature of the phase transitions are discussed in comparison to mean-field theory. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 77 |
| Issue: | 18 |
| Pages: | 184505 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-34828 |
| DOI: | 10.1103/PhysRevB.77.184505 |
| Nebis system number: | 001888782 |
Expansion of a Quantum Gas Released from an Optical Lattice
,
Gerbier, F., Trotzky, S., Fölling, S., Schnorrberger, U., Thompson, J. D., Widera, A., Bloch, I., Pollet, L., Troyer, M., Capogrosso-Sansone, B., Prokof'ev, N. V., Svistunov, B. V.,
2008
>>
| Author(s): | Gerbier, F., Trotzky, S., Fölling, S., Schnorrberger, U., Thompson, J. D., Widera, A., Bloch, I., Pollet, L., Troyer, M., Capogrosso-Sansone, B., Prokof'ev, N. V., Svistunov, B. V. |
| Title: | Expansion of a Quantum Gas Released from an Optical Lattice |
| Abstract: | We analyze the interference pattern produced by ultracold atoms released from an optical lattice. Such interference patterns are commonly interpreted as the momentum distributions of the trapped quantum gas. We show that for finite time-of-flights the resulting density distribution can, however, be significantly altered, similar to a near-field diffraction regime in optics. We illustrate our findings with a simple model and realistic quantum Monte Carlo simulations for bosonic atoms, and compare the latter to experiments. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 15 |
| Pages: | 155303-1 - 155303-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43932 |
| DOI: | 10.1103/PhysRevLett.101.155303 |
| Nebis system number: | 000003868 |
Phase diagram of He-4 adsorbed on graphite
,
Corboz, Philippe, Boninsegni, Massimo, Pollet, Lode, Troyer, Matthias,
2008
>>
| Author(s): | Corboz, Philippe, Boninsegni, Massimo, Pollet, Lode, Troyer, Matthias |
| Title: | Phase diagram of He-4 adsorbed on graphite |
| Abstract: | We present results of a theoretical study of He-4 films adsorbed on graphite based on the continuous space worm algorithm. In the first layer, we find a domain-wall phase and a (7/16) registered structure between the commensurate (1/3) and the incommensurate solid phases. For the second layer, we find only superfluid and incommensurate solid phases. The commensurate phase found in a previous simulation work is only observed if first-layer particles are kept fixed; it disappears upon explicitly including their zero-point fluctuations. No evidence of any "supersolid" phase is found. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 78 |
| Issue: | 24 |
| Pages: | 245414-1 - 245414-6 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | adsorption, commensurate-incommensurate transformations, helium films, phase diagrams |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | adsorption, commensurate-incommensurate transformations, helium films, phase diagrams |
| DBID source: | PP-43923 |
| DOI: | 10.1103/PhysRevB.78.245414 |
| Nebis system number: | 001888782 |
Binding of a He-3 impurity to a screw dislocation in solid He-4
,
Corboz, P., Pollet, L., Prokof'ev, N. V., Troyer, M.,
2008
>>
| Author(s): | Corboz, P., Pollet, L., Prokof'ev, N. V., Troyer, M. |
| Title: | Binding of a He-3 impurity to a screw dislocation in solid He-4 |
| Abstract: | Using first-principles simulations for the probability density of finding a He-3 atom in the vicinity of the screw dislocation in solid He-4, we determine the binding energy to the dislocation nucleus E-B=0.8 +/- 0.1 K and the density of localized states at larger distances. The specific heat due to He-3 features a peak similar to the one observed in recent experiments, and our model can also account for the observed increase in shear modulus at low temperature. We further discuss the role of He-3 in the picture of superfluid defects. |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 15 |
| Pages: | 155302-1 - 155302-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43924 |
| DOI: | 10.1103/PhysRevLett.101.155302 |
| Nebis system number: | 000003868 |
Critical Temperature Curve in BEC-BCS Crossover
,
Burovski, Evgeni, Kozik, Evgeny, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias,
2008
>>
| Author(s): | Burovski, Evgeni, Kozik, Evgeny, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias |
| Title: | Critical Temperature Curve in BEC-BCS Crossover |
| Abstract: | The strongly correlated regime of the crossover from Bardeen-Cooper-Schrieffer pairing to Bose-Einstein condensation can be realized by diluting a system of two-component fermions with a short-range attractive interaction. We investigate this system via a novel continuous-space-time diagrammatic determinant Monte Carlo method and determine the universal curve Tc/F for the transition temperature between the normal and the superfluid states as a function of the scattering length with the maximum on the Bose-Einstein condensation side. At unitarity, we confirm that Tc/F=0.152(7). |
| Published in: | Physical review letters |
| Volume: | 101 |
| Issue: | 9 |
| Pages: | 090402-1 - 090402-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-44240 |
| DOI: | 10.1103/PhysRevLett.101.090402 |
| Nebis system number: | 000003868 |
Quantum phase transition in a Heisenberg antiferromagnet on a square lattice with strong plaquette interactions
,
Albuquerque, A. Fabricio, Troyer, Matthias, Oitmaa, Jaan,
2008
>>
| Author(s): | Albuquerque, A. Fabricio, Troyer, Matthias, Oitmaa, Jaan |
| Title: | Quantum phase transition in a Heisenberg antiferromagnet on a square lattice with strong plaquette interactions |
| Abstract: | We present numerical results for an S=1/2 Heisenberg antiferromagnet on an inhomogeneous square lattice with tunable interaction between spins belonging to different plaquettes. Employing quantum Monte Carlo, we significantly improve on previous results for the critical point separating singlet-disordered and Néel-ordered phases and obtain an estimate for the critical exponent consistent with the three-dimensional classical Heisenberg universality class. Additionally, we show that a fairly accurate result for the critical point can be obtained from a contractor renormalization expansion by applying a surprisingly simple analysis to the effective Hamiltonian. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 78 |
| Issue: | 13 |
| Pages: | 132402-1 - 132402-4 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-43826 |
| DOI: | 10.1103/PhysRevB.78.132402 |
| Nebis system number: | 001888782 |
Engineering exotic phases for topologically protected quantum computation by emulating quantum dimer models
,
Albuquerque, A. Fabricio, Katzgraber, Helmut G., Troyer, Matthias, Blatter, Gianni,
2008
>>
| Author(s): | Albuquerque, A. Fabricio, Katzgraber, Helmut G., Troyer, Matthias, Blatter, Gianni |
| Title: | Engineering exotic phases for topologically protected quantum computation by emulating quantum dimer models |
| Abstract: | We use a nonperturbative extended contractor renormalization (ENCORE) method for engineering quantum devices for the implementation of topologically protected quantum bits described by an effective quantum dimer model on the triangular lattice. By tuning the couplings of the device, topological protection might be achieved if the ratio between effective two-dimer interactions and flip amplitudes lies in the liquid phase of the phase diagram of the quantum dimer model. For a proposal based on a quantum Josephson junction array [L. B. Ioffe , Nature (London) 415, 503 (2002)] our results show that optimal operational temperatures below 1 mK can only be obtained if extra interactions and dimer flips, which are not present in the standard quantum dimer model and involve three or four dimers, are included. It is unclear if these extra terms in the quantum dimer Hamiltonian destroy the liquid phase needed for quantum computation. Minimizing the effects of multidimer terms would require energy scales in the nano-Kelvin regime. An alternative implementation based on cold atomic or molecular gases loaded into optical lattices is also discussed, and it is shown that the small energy scales involved-implying long operational times-make such a device impractical. Given the many orders of magnitude between bare couplings in devices, and the topological gap, the realization of topological phases in quantum devices requires careful engineering and large bare interaction scales. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 78 |
| Issue: | 1 |
| Pages: | 014503 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2008-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Josephson effect, Optical lattices, Quantum computing, Renormalisation |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Josephson effect, Optical lattices, Quantum computing, Renormalisation |
| DBID source: | PP-34825, PP-41677 |
| DOI: | 10.1103/PhysRevB.78.014503 |
| Nebis system number: | 001888782 |
Optimized broad-histogram ensembles for the simulation of quantum systems
,
Wessel, Stefan, Stoop, Norbert, Gull, Emanuel, Trebst, Simon, Troyer, Matthias,
2007
>>
| Author(s): | Wessel, Stefan, Stoop, Norbert, Gull, Emanuel, Trebst, Simon, Troyer, Matthias |
| Title: | Optimized broad-histogram ensembles for the simulation of quantum systems |
| Abstract: | The efficiency of statistical sampling in broad-histogram Monte Carlo simulations can be considerably improved by optimizing the simulated extended ensemble for fastest equilibration. Here we describe how a recently developed feedback algorithm can be generalized to find optimized sampling distributions for the simulation of quantum systems in the context of the stochastic series expansion (SSE) when defining an extended ensemble in the expansion order. If the chosen update method is efficient, such as non-local updates for systems undergoing a second-order phase transition, the optimized ensemble is characterized by a flat histogram in the expansion order if a variable-length formulation of the SSE is used. Whenever the update method suffers from slowdown, such as at a first-order phase transition, the feedback algorithm shifts weight towards the expansion orders in the transition region, resulting in a non-uniform histogram. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2007 |
| Pages: | P12005-1 - P12005-28 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | quantum Monte Carlo simulations, analysis of algorithms |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | quantum Monte Carlo simulations, analysis of algorithms |
| DBID source: | PP-33833 |
| DOI: | 10.1088/1742-5468/2007/12/P12005 |
| Nebis system number: | 004699119 |
Breakdown of a topological phase
,
Trebst, Simon, Werner, Philipp, Troyer, Matthias, Shtengel, Kirill, Nayak, Chetan,
2007
>>
| Author(s): | Trebst, Simon, Werner, Philipp, Troyer, Matthias, Shtengel, Kirill, Nayak, Chetan |
| Title: | Breakdown of a topological phase |
| Subtitle: | Quantum phase transition in a loop gas model with tension |
| Abstract: | We study the stability of topological order against local perturbations by considering the effect of a magnetic field on a spin model—the toric code—which is in a topological phase. The model can be mapped onto a quantum loop gas where the perturbation introduces a bare loop tension. When the loop tension is small, the topological order survives. When it is large, it drives a continuous quantum phase transition into a magnetic state. The transition can be understood as the condensation of “magnetic” vortices, leading to confinement of the elementary “charge” excitations. We also show how the topological order breaks down when the system is coupled to an Ohmic heat bath and relate our results to error rates for topological quantum computations. |
| Published in: | Physical review letters |
| Volume: | 98 |
| Issue: | 7 |
| Pages: | 070602-1 - 070602-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26386 |
| DOI: | 10.1103/PhysRevLett.98.070602 |
| Nebis system number: | 000003868 |
Superfluidity of Grain Boundaries in Solid 4He
,
Pollet L., Boninsegni, M., Kuklov, A., Prokof'ev, N., Svistunov, S., Troyer, M.,
2007
>>
| Author(s): | Pollet L., Boninsegni, M., Kuklov, A., Prokof'ev, N., Svistunov, S., Troyer, M. |
| Title: | Superfluidity of Grain Boundaries in Solid 4He |
| Abstract: | By large-scale quantum Monte Carlo simulations we show that grain boundaries in 4He crystals are generically superfluid at low temperature, with a transition temperature of the order of ~0.5 K at the melting pressure; nonsuperfluid grain boundaries are found only for special orientations of the grains. We also find that close vicinity to the melting line is not a necessary condition for superfluid grain boundaries, and a grain boundary in direct contact with the superfluid liquid at the melting curve is found to be mechanically stable and the grain-boundary superfluidity observed by Sasaki et al. [Science 313, 1098 (2006)] is not just a crack filled with superfluid. |
| Published in: | Physical review letters |
| Volume: | 98 |
| Issue: | 13 |
| Pages: | 135301-1 - 135301-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-32782 |
| DOI: | 10.1103/PhysRevLett.98.135301 |
| Nebis system number: | 000003868 |
Self-consistent simulation of quantum wires defined by local oxidation of Ga(Al)As heterostructures
,
May, Christian P., Troyer, Matthias, Ensslin, Klaus,
2007
>>
| Author(s): | May, Christian P., Troyer, Matthias, Ensslin, Klaus |
| Title: | Self-consistent simulation of quantum wires defined by local oxidation of Ga(Al)As heterostructures |
| Abstract: | We calculate the electronic width of quantum wires as a function of their lithographic width in analogy to experiments performed on nanostructures defined by local oxidation of Ga(Al)As heterostructures. Two-dimensional simulations of two parallel oxide lines on top of a Ga(Al)As heterostructure defining a quantum wire are carried out in the framework of density functional theory in the local density approximation and are found to be in agreement with measurements. Quantitative assessment of the influence of various experimental uncertainties is given. The most influential parameter turns out to be the oxide line depth, followed by its exact shape and the effect of background doping (in decreasing order). |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 76 |
| Issue: | 23 |
| Pages: | 235321 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, aluminium compounds, density functional theory, gallium arsenide, III-V semiconductors, nanostructured materials, oxidation, semiconductor doping, semiconductor quantum wires |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | aluminium compounds, density functional theory, gallium arsenide, III-V semiconductors, nanostructured materials, oxidation, semiconductor doping, semiconductor quantum wires |
| DBID source: | PP-34824 |
| DOI: | 10.1103/PhysRevB.76.235321 |
| Nebis system number: | 001888782 |
Self-Consistent potential calculation for locally oxidized Ga[Al]As heterostructures
,
May, C., Ensslin, K., Troyer, M.,
2007
>>
| Author(s): | May, C., Ensslin, K., Troyer, M. |
| Title: | Self-Consistent potential calculation for locally oxidized Ga[Al]As heterostructures |
| Abstract: | We simulate the influence of local oxidation with an atomic force microscope (AFM) tip on the surface of a GaAlAs/GaAs heterostructure by means of numerical calculations. Assuming a rectangular shape of the oxide line, we solve the Schrodinger and Poisson equations self-consistently on a two-dimensional surface perpendicular to the oxide line. We observe that the distance between the two-dimensional electron gas (2DEG) and the surface is a crucial parameter for the electron density, confirming experimental 2DEG depletion results. |
| Published in: | Journal of computer-aided materials design |
| Volume: | 14 |
| Issue: | 1 |
| Pages: | 91 - 96 |
| ISSN: | 0928-1045, 1573-4900 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Semiconductor heterostructures, Ga[Al]As |
| Event name: | 1st International Conference on Synergy Between Experiment and Computation in Nanoscale Science |
| Event date: | May 31 - June 3, 2006 |
| Place: | Cambridge, MA, USA |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Semiconductor heterostructures, Ga[Al]As |
| DBID source: | PP-26825, PP-32675 |
| DOI: | 10.1007/s10820-006-9023-z |
| Nebis system number: | 000920009 |
Dimer-quadrupolar quantum phase transition in the quasi-one-dimensional Heisenberg model with biquadratic interactions
,
Harada, Kenji, Kawashima, Naoki, Troyer, Matthias,
2007
>>
| Author(s): | Harada, Kenji, Kawashima, Naoki, Troyer, Matthias |
| Title: | Dimer-quadrupolar quantum phase transition in the quasi-one-dimensional Heisenberg model with biquadratic interactions |
| Abstract: | The quasi-one-dimensional S=1 Heisenberg antiferromagnet with a biquadratic term is investigated at zero temperature by quantum Monte Carlo simulation. As the magnitude of the inter-chain coupling is increased, the system undergoes a phase transition from a spontaneously dimerized phase to a Néel ordered or spin nematic phase. The numerical results suggest the possibility of an unconventional second-order transition in which the symmetry group characterizing one phase is not a subgroup of the other. |
| Published in: | Journal of the Physical Society of Japan |
| Volume: | 76 |
| Pages: | 013703-1 - 013703-4 |
| ISSN: | 0031-9015, 1347-4073 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Tokyo |
| Publication status: | Published |
| Subjects: | Heisenberg model, quantum critical phenomena, Monte Carlo, quadrupole moment |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Heisenberg model, quantum critical phenomena, Monte Carlo, quadrupole moment |
| DBID source: | PP-26384 |
| DOI: | 10.1143/JPSJ.76.013703 |
| Nebis system number: | 000986184 |
Performance analysis of continuous-time solvers for quantum impurity models
,
Gull, Emanuel, Werner, Philipp, Millis, Andrew, Troyer, Matthias,
2007
>>
| Author(s): | Gull, Emanuel, Werner, Philipp, Millis, Andrew, Troyer, Matthias |
| Title: | Performance analysis of continuous-time solvers for quantum impurity models |
| Abstract: | Impurity solvers play an essential role in the numerical investigation of strongly correlated electrons systems within the “dynamical mean field” approximation. Recently, a new class of continuous-time solvers has been developed based on a diagrammatic expansion of the partition function in either the interactions or the impurity-bath hybridization. We investigate the performance of these two complementary approaches and compare them to the well-established Hirsch-Fye method. The results show that the continuous-time methods, and, in particular, the version which expands in the hybridization, provide substantial gains in computational efficiency. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 76 |
| Issue: | 23 |
| Pages: | 235123 |
| ISSN: | 1098-0121, 0163-1829, 1550-235X, 0556-2805 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Hubbard model, Impurities, Strongly correlated electron systems |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Hubbard model, Impurities, Strongly correlated electron systems |
| DBID source: | PP-26185, PP-32786 |
| DOI: | 10.1103/PhysRevB.76.235123 |
| Nebis system number: | 001888782 |
Quantum Monte Carlo study of a one-dimensional phase-fluctuating condensate in a harmonic trap
,
Gils, Charlotte, Pollet, Lode, Vernier, Alice, Hebert, Frederic, Batrouni, George, Troyer, Matthias,
2007
>>
| Author(s): | Gils, Charlotte, Pollet, Lode, Vernier, Alice, Hebert, Frederic, Batrouni, George, Troyer, Matthias |
| Title: | Quantum Monte Carlo study of a one-dimensional phase-fluctuating condensate in a harmonic trap |
| Abstract: | We study numerically the low temperature behavior of a one-dimensional Bose gas trapped in an optical lattice. For a sufficient number of particles and weak repulsive interactions, we find a clear regime of temperatures where density fluctuations are negligible but phase fluctuations are considerable, i.e., a quasicondensate. In the weakly interacting limit, our results are in very good agreement with those obtained using a mean-field approximation. In coupling regimes beyond the validity of mean-field approaches, a phase-fluctuating condensate also appears, but the phase-correlation properties are qualitatively different. It is shown that quantum depletion plays an important role. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 75 |
| Issue: | 6 |
| Pages: | 063631 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-32783 |
| DOI: | 10.1103/PhysRevA.75.063631 |
| Nebis system number: | 000619853 |
Absence of a structural glass phase in a monatomic model liquid predicted to undergo an ideal glass transition
,
Gils, Charlotte, Katzgraber, Helmut G., Troyer, Matthias,
2007
>>
| Author(s): | Gils, Charlotte, Katzgraber, Helmut G., Troyer, Matthias |
| Title: | Absence of a structural glass phase in a monatomic model liquid predicted to undergo an ideal glass transition |
| Abstract: | We study numerically a two- dimensional monodisperse model of interacting classical particles predicted to exhibit a static liquid - glass transition. Using a dynamical Monte Carlo method we show that the model does not freeze into a glassy phase at low temperatures. Instead, depending on the choice of the hard- core radius for the particles, the system either collapses trivially or a polycrystalline hexagonal structure emerges. |
| Published in: | Journal of statistical mechanics |
| Volume: | 07 |
| Pages: | P09011 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | classical Monte Carlo simulations, structural glasses (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | classical Monte Carlo simulations, structural glasses (theory) |
| DBID source: | PP-34826 |
| DOI: | 10.1088/1742-5468/2007/09/P09011 |
| Nebis system number: | 004699119 |
Interacting anyons in topological quantum liquids
,
Feiguin, Adrian, Trebst, Simon, Ludwig, Andreas W. W., Troyer, Matthias, Kitaev, Alexei, Wang, Zhenghan, Freedman, Michael H.,
2007
>>
| Author(s): | Feiguin, Adrian, Trebst, Simon, Ludwig, Andreas W. W., Troyer, Matthias, Kitaev, Alexei, Wang, Zhenghan, Freedman, Michael H. |
| Title: | Interacting anyons in topological quantum liquids |
| Subtitle: | The golden chain |
| Abstract: | We discuss generalizations of quantum spin Hamiltonians using anyonic degrees of freedom. The simplest model for interacting anyons energetically favors neighboring anyons to fuse into the trivial (“identity”) channel, similar to the quantum Heisenberg model favoring neighboring spins to form spin singlets. Numerical simulations of a chain of Fibonacci anyons show that the model is critical with a dynamical critical exponent z=1, and described by a two-dimensional (2D) conformal field theory with central charge c=(7/10). An exact mapping of the anyonic chain onto the 2D tricritical Ising model is given using the restricted-solid-on-solid representation of the Temperley-Lieb algebra. The gaplessness of the chain is shown to have topological origin. |
| Published in: | Physical Review Letters |
| Volume: | 98 |
| Issue: | 16 |
| Pages: | 160490-4 - 160490-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26396 |
| DOI: | 10.1103/PhysRevLett.98.160409 |
| Nebis system number: | 000003868 |
Recent results from the Gaussian Quantum Monte Carlo method for fermions with symmetry projection
,
Corboz, Philippe, Troyer, Matthias, Kleine, Adrian, McCulloch, Ian P., Schollwoeck, Ulrich, Assaad, F. F.,
2007
>>
| Author(s): | Corboz, Philippe, Troyer, Matthias, Kleine, Adrian, McCulloch, Ian P., Schollwoeck, Ulrich, Assaad, F. F. |
| Title: | Recent results from the Gaussian Quantum Monte Carlo method for fermions with symmetry projection |
| Abstract: | Gaussian Quantum Monte Carlo (GQMC) is a stochastic phase space method for fermions with positive weights. In the example of the Hubbard model close to half filling it fails to reproduce all the symmetries of the ground state leading to systematic errors at low temperatures. In a previous work [Phys. Rev. B {\bf 72}, 224518 (2005)] we proposed to restore the broken symmetries by projecting the density matrix obtained from the simulation onto the ground state symmetry sector. For ground state properties, the accuracy of this method depends on a {\it large overlap} between the GQMC and exact density matrices. Thus, the method is not rigorously exact. We present the limits of the approach by a systematic study of the method for 2 and 3 leg Hubbard ladders for different fillings and on-site repulsion strengths. We show several indications that the systematic errors stem from non-vanishing boundary terms in the partial integration step in the derivation of the Fokker-Planck equation. Checking for spiking trajectories and slow decaying probability distributions provides an important test of the reliability of the results. Possible solutions to avoid boundary terms are discussed. Furthermore we compare results obtained from two different sampling methods: Reconfiguration of walkers and the Metropolis algorithm. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 77 |
| Issue: | 8 |
| Pages: | 085108-1 - 085108-10 |
| ISSN: | 1098-0121, 0163-1829 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-35140, PP-32787 |
| DOI: | 10.1103/PhysRevB.77.085108 |
| Nebis system number: | 001888782 |
Luttinger liquid in the core of a screw dislocation in helium-4
,
Boninsegni, M., Kuklov, A. B., Pollet, L., Prokof'ev, N. V., Svistunov, B. V., Troyer, M.,
2007
>>
| Author(s): | Boninsegni, M., Kuklov, A. B., Pollet, L., Prokof'ev, N. V., Svistunov, B. V., Troyer, M. |
| Title: | Luttinger liquid in the core of a screw dislocation in helium-4 |
| Abstract: | On the basis of first-principles Monte Carlo simulations we find that the screw dislocation along the hexagonal axis of an hcp 4He crystal features a superfluid (at T → 0) core. This is the first example of a regular quasi-one-dimensional supersolid-the phase featuring both translational and superfluid orders, and one of the cleanest cases of a Luttinger-liquid system. In contrast, the same type of screw dislocation in solid H2 is insulating. |
| Published in: | Physical review letters |
| Volume: | 99 |
| Issue: | 3 |
| Pages: | 035301-1 - 035301-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-32784 |
| DOI: | 10.1103/PhysRevLett.99.035301 |
| Nebis system number: | 000003868 |
The ALPS project release 1.3
,
ALPS Collaboration, Albuquerque, A.F., et al., Corboz, P., Dayal, P., Gamper, L., Gull, E., Körner, M., Matsumoto, M., Pollet, L., Troyer, Matthias,
2007
>>
| Author(s): | ALPS Collaboration, Albuquerque, A.F., et al., Corboz, P., Dayal, P., Gamper, L., Gull, E., Körner, M., Matsumoto, M., Pollet, L., Troyer, Matthias |
| Title: | The ALPS project release 1.3 |
| Subtitle: | Open-source software for strongly correlated systems |
| Abstract: | We present release 1.3 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an international open-source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. Development is centered on common XML and binary data formats, on libraries to simplify and speed up code development, and on full-featured simulation programs. The programs enable non-experts to start carrying out numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), as well as the density matrix renormalization group (DMRG). Changes in the new release include a DMRG program for interacting models, support for translation symmetries in the diagonalization programs, the ability to define custom measurement operators, and support for inhomogeneous systems, such as lattice models with traps. The software is available from our web server at http://alps.comp-phys.org/. |
| Published in: | Journal of magnetism and magnetic materials |
| Volume: | 310 |
| Issue: | 2 |
| Pages: | 1187 - 1193 |
| ISSN: | 0304-8853 |
| Publication date / Date received: | 2007-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Quantum lattice model, Open-source software, C++, Monte Carlo, Quantum Monte Carlo, Density matrix renormalization group, DMRG, Exact diagonalization |
| Event name: | 17th International Conference on Magnetism ICM |
| Event date: | August 20-25, 2006 |
| Place: | Kyoto, Japan |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Quantum lattice model, Open-source software, C++, Monte Carlo, Quantum Monte Carlo, Density matrix renormalization group, DMRG, Exact diagonalization |
| DBID source: | PP-26385 |
| DOI: | 10.1016/j.jmmm.2006.10.304 |
| Nebis system number: | 000000398 |
Continuous-time solver for quantum impurity models
,
Werner, Philipp, Comanac, Armin, Medici, Luca de', Troyer, Matthias, Millis, Andrew J.,
2006
>>
| Author(s): | Werner, Philipp, Comanac, Armin, Medici, Luca de', Troyer, Matthias, Millis, Andrew J. |
| Title: | Continuous-time solver for quantum impurity models |
| Abstract: | We present a new continuous-time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on a stochastic sampling of a perturbation expansion in the impurity-bath hybridization parameter. Comparisons with Monte Carlo and exact diagonalization calculations confirm the accuracy of the new approach, which allows very efficient simulations even at low temperatures and for strong interactions. As examples of the power of the method we present results for the temperature dependence of the kinetic energy and the free energy, enabling an accurate location of the temperature-driven metal-insulator transition. |
| Published in: | Physical review letters |
| Volume: | 97 |
| Issue: | 7 |
| Pages: | 076405 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-18357, WOS-000239842100044 |
| DOI: | 10.1103/PhysRevLett.97.076405 |
| Nebis system number: | 000003868 |
Optimized parallel tempering simulations of proteins
,
Trebst, Simon, Troyer, Matthias, Hansmann, Ulrich H.E.,
2006
>>
| Author(s): | Trebst, Simon, Troyer, Matthias, Hansmann, Ulrich H.E. |
| Title: | Optimized parallel tempering simulations of proteins |
| Abstract: | We apply a recently developed adaptive algorithm that systematically improves the efficiency of parallel tempering or replica exchange methods in the numerical simulation of small proteins. Feedback iterations allow us to identify an optimal set of temperatures/replicas which are found to concentrate at the bottlenecks of the simulations. A measure of convergence for the equilibration of the parallel tempering algorithm is discussed. We test our algorithm by simulating the 36-residue villin headpiece subdomain HP-36 where we find a lowest-energy configuration with a root-mean-square deviation of less than 4 A to the experimentally determined structure. |
| Published in: | The journal of chemical physics |
| Volume: | 124 |
| Issue: | 17 |
| Pages: | 174903 |
| ISSN: | 0021-9606, 1089-7690 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Melville, NY |
| Publication status: | Published |
| Subjects: | Chemie allgemein|Chemistry, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-18363, WOS-000237321700042 |
| DOI: | 10.1063/1.2186639 |
| Nebis system number: | 000049290 |
D-wave resonating valence bond states of fermionic atoms in optical lattices
,
Trebst, Simon, Schollwöck, Ulrich, Troyer, Matthias, Zoller, Peter,
2006
>>
| Author(s): | Trebst, Simon, Schollwöck, Ulrich, Troyer, Matthias, Zoller, Peter |
| Title: | D-wave resonating valence bond states of fermionic atoms in optical lattices |
| Abstract: | We study controlled generation and measurement of superfluid d-wave resonating valence bond (RVB) states of fermionic atoms in 2D optical lattices. Starting from loading spatial and spin patterns of atoms in optical superlattices as pure quantum states from a Fermi gas, we adiabatically transform this state to an RVB state by a change of the lattice parameters. Results of exact time-dependent numerical studies for ladders systems are presented, suggesting generation of RVB states on a time scale smaller than typical experimental decoherence times. |
| Published in: | Physical review letters |
| Volume: | 96 |
| Issue: | 25 |
| Pages: | 250402 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-18359, WOS-000238697000002 |
| DOI: | 10.1103/PhysRevLett.96.250402 |
| Nebis system number: | 000003868 |
Phase diagram of Bose-Fermi mixtures in one-dimensional optical lattices
,
Pollet, Lode, Troyer, Matthias, Van Houcke, Kris, Rombouts, Stefan M.A.,
2006
>>
| Author(s): | Pollet, Lode, Troyer, Matthias, Van Houcke, Kris, Rombouts, Stefan M.A. |
| Title: | Phase diagram of Bose-Fermi mixtures in one-dimensional optical lattices |
| Abstract: | The ground state phase diagram of the one-dimensional Bose-Fermi Hubbard model is studied in the canonical ensemble using a quantum Monte Carlo method. We focus on the case where both species have half filling in order to maximize the pairing correlations between the bosons and the fermions. In case of equal hopping we distinguish among phase separation, a Luttinger liquid phase, and a phase characterized by strong singlet pairing between the species. True long-range density waves exist with unequal hopping amplitudes. |
| Published in: | Physical review letters |
| Volume: | 96 |
| Issue: | 19 |
| Pages: | 190402 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-18349, WOS-000237683600003 |
| DOI: | 10.1103/PhysRevLett.96.190402 |
| Nebis system number: | 000003868 |
Wang-Landau sampling with cluster updates
,
Körner, M., Troyer, M.,
2006
>>
| Author(s): | Körner, M., Troyer, M. |
| Title: | Wang-Landau sampling with cluster updates |
| Abstract: | We present a new algorithm, combining cluster updates with Wang-Landau sampling and compare the performance to local updates. |
| Book title: | Computer simulation studies in condensed-matter physics XVI [i.e. XVII] : proceedings of the seventeenth workshop, Athens, GA, USA, February 16-20, 2004 |
| Published in: | Springer Proceedings in Physics |
| Volume: | 103 |
| Pages: | 142 - 145 |
| ISBN: | 3-540-26564-3, 978-3-540-26564-1, 9783540265658 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Theoretische Physik und numerische Methoden|Theoretical Physics and Numerical Methods, Kondensierte Materie|Condensed Matter |
| Event name: | 17th Workshop on Computer Simulation Studies in Condensed-Matter Physics |
| Event date: | February 16-20, 2004 |
| Place: | Athens, GA, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000236265500016 |
| DOI: | 10.1007/b137808 |
| Nebis system number: | 005135458 |
Deconfined criticality, runaway flow in the two-component scalar electrodynamics and weak first-order superfluid-solid transitions
,
Kuklov, A.B., Prokof'ev, N.V., Svistunov, B.V., Troyer, M.,
2006
>>
| Author(s): | Kuklov, A.B., Prokof'ev, N.V., Svistunov, B.V., Troyer, M. |
| Title: | Deconfined criticality, runaway flow in the two-component scalar electrodynamics and weak first-order superfluid-solid transitions |
| Abstract: | We perform a comparative Monte Carlo study of the easy-plane deconfined critical point (DCP) action and its short-range counterpart to reveal close similarities between the two models for intermediate and strong coupling regimes. For weak coupling, the structure of the phase diagram depends on the interaction range: while the short-range model features a tricritical point and a continuous U(1) × U(1) transition, the long-range DCP action is characterized by the runaway renormalization flow of coupling into a first (I) order phase transition. We develop a “numerical flowgram” method for high precision studies of the runaway effect, weakly I-order transitions, and polycritical points. We prove that the easy-plane DCP action is the field theory of a weakly I-order phase transition between the valence bond solid and the easy-plane antiferromagnet (or superfluid, in particle language) for any value of the weak coupling strength. Our analysis also solves the long standing problem of what is the ultimate fate of the runaway flow to strong coupling in the theory of scalar electrodynamics in three dimensions with U(1) × U(1) symmetry of quartic interactions. |
| Published in: | Annals of physics |
| Volume: | 321 |
| Issue: | 7 |
| Pages: | 1602 - 1621 |
| ISSN: | 0003-4916 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Quantum phase transitions, Scaling, Deconfined critical point |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Quantum phase transitions, Scaling, Deconfined critical point |
| DBID source: | PP-26383, WOS-000238823000008 |
| DOI: | 10.1016/j.aop.2006.04.007 |
| Nebis system number: | 000042350 |
Feedback-optimized parallel tempering Monte Carlo
,
Katzgraber, Helmut G., Trebst, Simon, Huse, David A., Troyer, Matthias,
2006
>>
| Author(s): | Katzgraber, Helmut G., Trebst, Simon, Huse, David A., Troyer, Matthias |
| Title: | Feedback-optimized parallel tempering Monte Carlo |
| Abstract: | We introduce an algorithm for systematically improving the efficiency of parallel tempering Monte Carlo simulations by optimizing the simulated temperature set. Our approach is closely related to a recently introduced adaptive algorithm that optimizes the simulated statistical ensemble in generalized broad-histogram Monte Carlo simulations. Conventionally, a temperature set is chosen in such a way that the acceptance rates for replica swaps between adjacent temperatures are independent of the temperature and large enough to ensure frequent swaps. In this paper, we show that by choosing the temperatures with a modified version of the optimized ensemble feedback method we can minimize the round-trip times between the lowest and highest temperatures which effectively increases the efficiency of the parallel tempering algorithm. In particular, the density of temperatures in the optimized temperature set increases at the 'bottlenecks' of the simulation, such as phase transitions. In turn, the acceptance rates are now temperature dependent in the optimized temperature ensemble. We illustrate the feedback-optimized parallel tempering algorithm by studying the two-dimensional Ising ferromagnet and the two-dimensional fully frustrated Ising model, and briefly discuss possible feedback schemes for systems that require configurational averages, such as spin glasses. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2006 |
| Issue: | 3 |
| Pages: | P03018 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Classical Monte Carlo simulations, Other numerical approaches, Analysis of algorithms |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Classical Monte Carlo simulations, Other numerical approaches, Analysis of algorithms |
| DBID source: | PP-26380, PP-26572 |
| DOI: | 10.1088/1742-5468/2006/03/P03018 |
| Nebis system number: | 004699119 |
Ramping fermions in optical lattices across a Feshbach resonance
,
Katzgraber, Helmut G., Esposito, Aniello, Troyer, Matthias,
2006
>>
| Author(s): | Katzgraber, Helmut G., Esposito, Aniello, Troyer, Matthias |
| Title: | Ramping fermions in optical lattices across a Feshbach resonance |
| Abstract: | We study the properties of ultracold Fermi gases in a three-dimensional optical lattice when crossing a Feshbach resonance. By using a zero-temperature formalism, we show that three-body processes are enhanced in a lattice system in comparison to the continuum case. This poses one possible explanation for the short molecule lifetimes found when decreasing the magnetic field across a Feshbach resonance. Effects of finite temperatures on the molecule formation rates are also discussed by computing the fraction of double-occupied sites. Our results show that current experiments are performed at temperatures considerably higher than expected: lower temperatures are required for fermionic systems to be used to simulate quantum Hamiltonians. In addition, by relating the double occupancy of the lattice to the temperature, we provide a means for thermometry in fermionic lattice systems, previously not accessible experimentally. The effects of ramping a filled lowest band across a Feshbach resonance when increasing the magnetic field are also discussed: fermions are lifted into higher bands due to entanglement of Bloch states, in good agreement with recent experiments. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 74 |
| Issue: | 4 |
| Pages: | 43602 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Subjects: | Fermion systems, Resonant states, Laser cooling |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Fermion systems, Resonant states, Laser cooling |
| DBID source: | PP-18339, WOS-000241723100136 |
| DOI: | 10.1103/PhysRevA.74.043602 |
| Nebis system number: | 000619853 |
Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps
,
Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George,
2006
>>
| Author(s): | Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George |
| Title: | Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps |
| Abstract: | We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining potentials. The quantum criticality of the superfluid-Mott insulator transition is investigated both on the boundary layer separating the two coexisting phases and at the center of the traps where the Mott-insulating phase is first established. Recent simulations of systems in quadratic traps have shown that the transition is not in the critical regime due to the finite gradient of the confining potential and that critical fluctuations are suppressed. In addition, it has been shown that quantum critical behavior is recovered in flat confining potentials as they approach the uniform regime. Our results show that quartic traps display a behavior similar to quadratic ones, yet locally at the center of the traps the bulk transition has enhanced critical fluctuations in comparison to the quadratic case. Therefore quartic traps provide a better prerequisite for the experimental observation of true quantum criticality of ultracold bosonic atoms in optical lattices. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 73 |
| Issue: | 6 |
| Pages: | 63606 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-18366, WOS-000238694900132 |
| DOI: | 10.1103/PhysRevA.73.063606 |
| Nebis system number: | 000619853 |
A massively parallel particle-in-cell code for the simulation of field-emitter based electron sources
,
Candel, Arno E., Dehler, Micha M., Troyer, Matthias,
2006
>>
| Author(s): | Candel, Arno E., Dehler, Micha M., Troyer, Matthias |
| Title: | A massively parallel particle-in-cell code for the simulation of field-emitter based electron sources |
| Abstract: | For the realistic simulation of electron sources using field emitter arrays, the sub-micron resolution required for the emitters leads to simulation models not suitable for current serial codes. Thus, a parallel high-performance 3D Particle-In-Cell code, called Capone, has been implemented in C++ using the POOMA II framework on the Linux platform. Sophisticated C++ expression templates techniques deliver Fortran performance combined with high-level programming and development comfort. For the computation of external fields, matching parallel field solvers are in development with the electrostatic one being completed. The Maxwell field solver is based on the Finite Integration Algorithm on a non-uniform rectilinear grid. Anisotropic ε and μ constants and perfect electric/magnetic materials stored in triangulated grid cells are supported as well as open, electric and magnetic boundary conditions. Self-consistent macro-particle pushing is accomplished by integrating the classical relativistic equations of motion in combination with charge-conserving current scattering onto the computational grid. Parallelization is performed by partitioning the calculation domain into patches associated to individual processors. Fields are statically distributed while Particles are concurrently distributed to processors according to their position to allow fast local interpolation. |
| Published in: | Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment |
| Volume: | 558 |
| Issue: | 1 |
| Pages: | 154 - 158 |
| ISSN: | 0168-9002 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Electromagnetism, Charged-particle beam, Free-electron lasers, Computer simulation, Maxwell, Self-consistent, Particle dynamics, Particle-In-Cell, Time-domain, Parallel computing, C++ |
| Event name: | 8th International Computational Accelerator Physics Conference (ICAP 2004) |
| Event date: | June 29 - July 2, 2004 |
| Place: | St. Petersburg, Russia |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Electromagnetism, Charged-particle beam, Free-electron lasers, Computer simulation, Maxwell, Self-consistent, Particle dynamics, Particle-In-Cell, Time-domain, Parallel computing, C++ |
| DBID source: | PP-9384, WOS-000236162200033 |
| DOI: | 10.1016/j.nima.2005.11.059 |
| Nebis system number: | 000029139 |
The Fermi-Hubbard model at unitarity
,
Burovski, Evgeni, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias,
2006
>>
| Author(s): | Burovski, Evgeni, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias |
| Title: | The Fermi-Hubbard model at unitarity |
| Abstract: | We simulate the dilute attractive Fermi - Hubbard model in the unitarity regime using a diagrammatic determinant Monte Carlo ( MC) algorithm with worm-type updates. We obtain the dependence of the critical temperature on the filling factor. and, by extrapolating to nu --> 0, determine the universal critical temperature of the continuum unitary Fermi gas in units of Fermi energy: T-c/epsilon(F) = 0.152( 7). We also determine the thermodynamic functions and show how the MC results can be used for accurate thermometry of a trapped unitary gas. |
| Published in: | New journal of physics |
| Volume: | 8 |
| Issue: | 153 |
| Pages: | 1 - 30 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26382, WOS-000240206900004 |
| DOI: | 10.1088/1367-2630/8/8/153 |
| Nebis system number: | 001997538 |
Critical Temperature and Thermodynamics of Attractive Fermions at Unitarity
,
Burovski, Evgeni, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias,
2006
>>
| Author(s): | Burovski, Evgeni, Prokof'ev, Nikolay, Svistunov, Boris, Troyer, Matthias |
| Title: | Critical Temperature and Thermodynamics of Attractive Fermions at Unitarity |
| Abstract: | The unitarity regime of the BCS-BEC crossover can be realized by diluting a system of two-component lattice fermions with an on-site attractive interaction. We perform a systematic-error-free finite-temperature simulation of this system by diagrammatic determinant Monte Carlo method. The critical temperature in units of Fermi energy is found to be Tc/epsilonF=0.152(7). We also report the behavior of the thermodynamic functions, and discuss the issues of thermometry of ultracold Fermi gases. |
| Published in: | Physical review letters |
| Volume: | 96 |
| Issue: | 16 |
| Pages: | 160402 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26381, WOS-000237156700002 |
| DOI: | 10.1103/PhysRevLett.96.160402 |
| Nebis system number: | 000003868 |
Fate of Vacancy-Induced Supersolidity in 4He
,
Boninsegni, M., Kuklov, A. B., Pollet, L., Prokof'ev, N. V., Svistunov, B. V., Troyer, M.,
2006
>>
| Author(s): | Boninsegni, M., Kuklov, A. B., Pollet, L., Prokof'ev, N. V., Svistunov, B. V., Troyer, M. |
| Title: | Fate of Vacancy-Induced Supersolidity in 4He |
| Abstract: | The supersolid state of matter, exhibiting nondissipative flow in solids, has been elusive for 35 years. The recent discovery of a nonclassical moment of inertia in solid 4He by Kim and Chan provided the first experimental evidence, although the interpretation in terms of supersolidity of the ideal crystal phase remains a subject to debate. Using quantum Monte Carlo methods we investigate the long-standing question of vacancy-induced superflow and find that vacancies in a 4He crystal phase separate instead of forming a supersolid. On the other hand, nonequilibrium vacancies relaxing on defects of polycrystalline samples could provide an explanation for the experimental observations. |
| Published in: | Physical review letters |
| Volume: | 97 |
| Issue: | 8 |
| Pages: | 080401 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | PP-26272, WOS-000240043800001 |
| DOI: | 10.1103/PhysRevLett.97.080401 |
| Nebis system number: | 000003868 |
Gaussian Quantum Monte Carlo methods with symmetry projection
,
Assaad, F. F., Corboz, P., Gull, E., Petersen, Wesley P., Troyer, M., Werner, P.,
2006
>>
| Author(s): | Assaad, F. F., Corboz, P., Gull, E., Petersen, Wesley P., Troyer, M., Werner, P. |
| Title: | Gaussian Quantum Monte Carlo methods with symmetry projection |
| Abstract: | Recently Corney and Drummond introduced the sign-free Gaussian Quantum Monte Carlo method (GQMC) for the Hubbard model. We generalize their ideas to derive stochastic differential equations (SDEs) for the general electronic structure problem. We show that the method fails to reproduce the correct symmetries of the ground state leading to systematic errors at low temperatures. We propose to restore these symmetries a posteriori by projecting the resulting density matrix onto the symmetry sectors of the ground state. The so produced results are accurate and reliable, even for parameters where an auxiliary field QMC approach fails due to a severe sign problem. Possible sources for the systematic errors are discussed. |
| Book title: | Effective models for low-dimensional strongly correlated systems : Peyresq, France, 12-16 September 2005 |
| Published in: | AIP conference proceedings |
| Volume: | 816 |
| Pages: | 204 - 231 |
| ISBN: | 0-7354-0309-0, 978-0-7354-0309-3 |
| Publication date / Date received: | 2006-01-01 |
| Publication status: | Melville, N.Y. |
| Publication status: | Published |
| Subjects: | Kondensierte Materie|Condensed Matter, Hubbard model, general electronic structure problem, quantum Monte Carlo, sign problem, stochastic phase space method |
| Event name: | Meeting on Effective Models for Low-Dimensional Strongly Correlated Systems |
| Event date: | September 12-16, 2005 |
| Place: | Peyresq, France |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Hubbard model, general electronic structure problem, quantum Monte Carlo, sign problem, stochastic phase space method |
| DBID source: | PP-26251 |
| DOI: | 10.1063/1.2178044 |
| Nebis system number: | 005172502 |
Neel temperature of quasi-low-dimensional Heisenberg antiferromagnets
,
Yasuda, C., Todo, S., Hukushima, K., Alet, Fabien, Keller, M., Troyer, Matthias, Takayama, H.,
2005
>>
| Author(s): | Yasuda, C., Todo, S., Hukushima, K., Alet, Fabien, Keller, M., Troyer, Matthias, Takayama, H. |
| Title: | Neel temperature of quasi-low-dimensional Heisenberg antiferromagnets |
| Abstract: | The Neel temperature T-N of quasi-one- and quasi-two-dimensional antiferromagnetic Heisenberg models on a cubic lattice is calculated by Monte Carlo simulations as a function of interchain (interlayer) to intrachain (intralayer) coupling J(')/J down to J(')/J similar or equal to 10(-3). We find that T-N obeys a modified random-phase approximationlike relation for small J(')/J with an effective universal renormalized coordination number, independent of the size of the spin. Empirical formulas describing T-N for a wide range of J(') and useful for the analysis of experimental measurements are presented. |
| Published in: | Physical review letters |
| Volume: | 94 |
| Issue: | 21 |
| Pages: | 217201 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000229543900038, PP-955 |
| DOI: | 10.1103/PhysRevLett.94.217201 |
| Nebis system number: | 000003868 |
Overcoming the slowing down of flat-histogram Monte Carlo simulations
,
Wu, Yong, Körner, Mathias, Colonna-Romano, Louis, Trebst, Simon, Gould, harvey, Machta, Jonathan, Troyer, Matthias,
2005
>>
| Author(s): | Wu, Yong, Körner, Mathias, Colonna-Romano, Louis, Trebst, Simon, Gould, harvey, Machta, Jonathan, Troyer, Matthias |
| Title: | Overcoming the slowing down of flat-histogram Monte Carlo simulations |
| Subtitle: | Cluster updates and optimized broad-histogram ensembles |
| Abstract: | We study the performance of Monte Carlo simulations that sample a broad histogram in energy by determining the mean first-passage time to span the entire energy space of d-dimensional ferromagnetic Ising/Potts models. We first show that flat-histogram Monte Carlo methods with single-spin flip updates such as the Wang-Landau algorithm or the multicanonical method perform suboptimally in comparison to an unbiased Markovian random walk in energy space. For the d=1, 2, 3 Ising model, the mean first-passage time tau scales with the number of spins N=L-d as tau proportional to (NLz)-L-2. The exponent z is found to decrease as the dimensionality d is increased. In the mean-field limit of infinite dimensions we find that z vanishes up to logarithmic corrections. We then demonstrate how the slowdown characterized by z>0 for finite d can be overcome by two complementary approaches-cluster dynamics in connection with Wang-Landau sampling and the recently developed ensemble optimization technique. Both approaches are found to improve the random walk in energy space so that tau proportional to N-2 up to logarithmic corrections for the d=1, 2 Ising model. |
| Published in: | Physical review E, Statistical, nonlinear, and soft matter physics |
| Volume: | 72 |
| Issue: | 4 |
| Pages: | 046704 |
| ISSN: | 1539-3755, 1063-651X, 1095-3787, 1550-2376 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000232931200115, PP-9358 |
| DOI: | 10.1103/PhysRevE.72.046704a |
| Nebis system number: | 004109079 |
Supersolid Hard-Core Bosons on the Triangular Lattice
,
Wessel, Stefan, Troyer, Matthias,
2005
>>
| Author(s): | Wessel, Stefan, Troyer, Matthias |
| Title: | Supersolid Hard-Core Bosons on the Triangular Lattice |
| Abstract: | We determine the phase diagram of hard-core bosons on a triangular lattice with nearest-neighbor repulsion, paying special attention to the stability of the supersolid phase. Similar to the same model on a square lattice we find that for densities rho < 1/3 or rho > 2/3 a supersolid phase is unstable and the transition between a commensurate solid and the superfluid is of first order. At intermediate fillings 1/3 |
| Published in: | Physical review letters |
| Volume: | 95 |
| Issue: | 12 |
| Pages: | ARTN 127205 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000231908200053 |
| DOI: | 10.1103/PhysRevLett.95.127205 |
| Nebis system number: | 000003868 |
A renormalization approach to simulations of quantum effects in nanoscale magnetic systems
,
Wessel, S., Trebst, S., Troyer, M.,
2005
>>
| Author(s): | Wessel, S., Trebst, S., Troyer, M. |
| Title: | A renormalization approach to simulations of quantum effects in nanoscale magnetic systems |
| Abstract: | Simulation of the dynamics of nanoscale systems are usually restricted to a purely classical description, which becomes inadequate once technological minimization reaches scales on which quantum mechanical effects become relevant. In this paper we propose a multiscale approach to estimate quantum corrections to such classical descriptions. Quantum fluctuations in a quantum magnet are absorbed into thermal fluctuations by a locally varying renormalization of the corresponding classical magnet. To obtain these renormalization factors we match results of a quantum Monte Carlo simulation to classical Monte Carlo simulations. Using error robust optimization methods, such as simplex and genetic algorithms, we obtain an optimal set of renormalized couplings of the classical magnet which exhibits the same properties as the quantum magnet. A spatially varying renormalization takes into account the larger quantum fluctuations in the vicinity of surfaces and magnetic interfaces. We discuss applications of the algorithm to multiscale simulations of the dynamics of magnetic systems. |
| Published in: | Multiscale modeling & simulation |
| Volume: | 4 |
| Issue: | 1 |
| Pages: | 237 - 249 |
| ISSN: | 1540-3459, 1540-3467 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Philadelphia, PA |
| Publication status: | Published |
| Subjects: | Angewandte Informatik, Künstliche Intelligenz|Applied Computer Science, Artificial Intelligence, Quantum effects, Magnetic systems, Monte Carlo simulations |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Quantum effects, Magnetic systems, Monte Carlo simulations |
| DBID source: | WOS-000230501900010 |
| DOI: | 10.1137/03060206X |
| Nebis system number: | 004481084 |
Bosons in optical lattices – from the Mott transition to the Tonks–Girardeau gas
,
Wessel, S., Alet, F., Trebst, S., Leumann, D., Troyer, M., Batrouni, G.G.,
2005
>>
| Author(s): | Wessel, S., Alet, F., Trebst, S., Leumann, D., Troyer, M., Batrouni, G.G. |
| Title: | Bosons in optical lattices – from the Mott transition to the Tonks–Girardeau gas |
| Abstract: | We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, focusing on the crossover from a gas of softcore bosons to a Tonks–Girardeau gas in a one-dimensional optical lattice. We find that depending on the quantity being measured, the behavior found in the Tonks–Girardeau regime is observed already at relatively small values of the interaction strength. A finite critical value for entering the Tonks–Girardeau regime does not exist. Furthermore, we discuss the computational efficiency of two quantum Monte Carlo methods to simulate large scale trapped bosonic systems: directed loops in stochastic series expansions and the worm algorithm. |
| Published in: | Journal of the Physical Society of Japan |
| Volume: | 74 |
| Pages: | 10 - 15 |
| ISSN: | 0031-9015, 1347-4073 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Tokyo |
| Publication status: | Published |
| Subjects: | boson Hubbard model, quantum Monte Carlo, cold atoms, optical lattice, hard-core bosons, Tonks–Girardeau gas |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | boson Hubbard model, quantum Monte Carlo, cold atoms, optical lattice, hard-core bosons, Tonks–Girardeau gas |
| DBID source: | PP-9354 |
| Nebis system number: | 000986184 |
Phase Diagram and Critical Exponents of a Dissipative Ising Spin Chain in a Transverse Magnetic Field
,
Werner, Philipp, Völker, Klaus, Troyer, Matthias, Chakravarty, Sudip,
2005
>>
| Author(s): | Werner, Philipp, Völker, Klaus, Troyer, Matthias, Chakravarty, Sudip |
| Title: | Phase Diagram and Critical Exponents of a Dissipative Ising Spin Chain in a Transverse Magnetic Field |
| Abstract: | We consider a one-dimensional Ising model in a transverse magnetic field coupled to a dissipative heat bath. The phase diagram and the critical exponents are determined from extensive Monte Carlo simulations. It is shown that the character of the quantum phase transition is radically altered from the corresponding nondissipative model and the double well coupled to a dissipative heat bath with linear friction. Spatial couplings and the dissipative dynamics combine to form a new quantum criticality which is independent of dissipation strength. |
| Published in: | Physical review letters |
| Volume: | 94 |
| Issue: | 4 |
| Pages: | 047201 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000226779000057, PP-9351, PP-9362 |
| DOI: | 10.1103/PhysRevLett.94.047201 |
| Nebis system number: | 000003868 |
Quantum spin chains with site dissipation
,
Werner, Philipp, Troyer, Matthias, Sachdev, Subir,
2005
>>
| Author(s): | Werner, Philipp, Troyer, Matthias, Sachdev, Subir |
| Title: | Quantum spin chains with site dissipation |
| Abstract: | We use Monte Carlo simulations to study chains of Ising- and XY-spins with dissipationcoupling to the site variables. The phase diagram and critical exponents of the dissipative Ising chain in a transverse magnetic field have been computed previously, and here we consider a universal ratio of susceptibilities. We furthermore present the phase diagram and exponents of the dissipative XY-chain, which exhibits a second order phase transition. All our results compare well with the predictions from a dissipative φ4 field theory. |
| Published in: | Journal of the Physical Society of Japan. Supplement |
| Volume: | 74 |
| Pages: | 67 - 70 |
| ISSN: | 0375-9598 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Tokyo |
| Publication status: | Published |
| Subjects: | spin chains, dissipation, phase transition, Monte Carlo |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | spin chains, dissipation, phase transition, Monte Carlo |
| DBID source: | PP-9353 |
| Nebis system number: | 005223014 |
Efficient simulation of resistively shunted josephson junctions
,
Werner, Philipp, Troyer, Matthias,
2005
>>
| Author(s): | Werner, Philipp, Troyer, Matthias |
| Title: | Efficient simulation of resistively shunted josephson junctions |
| Abstract: | We present a cluster algorithm for resistively shunted Josephson junctions or similar physical systems, which dramatically improves sampling efficiency, and apply it to the superconductor-to-metal transition in a single junction. Measuring the temperature dependence of the zero bias resistance, we confirm that the critical point does not depend on the strength of the Josephson coupling. However, we find that the correlation exponents vary continuously along the phase boundary, indicating that the Schmid-Bulgadaev transition is a line of fixed points. |
| Published in: | Physical review letters |
| Volume: | 95 |
| Issue: | 6 |
| Pages: | 060201 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000231017700001, PP-9357 |
| DOI: | 10.1103/PhysRevLett.95.060201 |
| Nebis system number: | 000003868 |
Effective charging energy of the single-electron box
,
Werner, Philipp, Troyer, Matthias,
2005
>>
| Author(s): | Werner, Philipp, Troyer, Matthias |
| Title: | Effective charging energy of the single-electron box |
| Abstract: | We present numerical results on electron tunnelling in a single-electron box at low temperature. The effective action of this device is equivalent to the Hamiltonian of a classical XY spin chain with long-ranged interactions. Using an efficient cluster algorithm and a new transition matrix Monte Carlo approach, we are able to compute the effective charging energy E-C* in the limit of very small tunnelling resistance. While previous Monte Carlo simulations were restricted to the weak- and intermediate-tunnelling regimes, our method extends the range of E-C*-values by more than 30 orders of magnitude. This allows us to clearly observe the exponential suppression of E-C* with increasing tunnelling conductance alpha. For large but fixed alpha, the correction to the leading exponential behaviour exhibits a crossover from an intermediate-temperature behaviour at betaE(C)* much less than 1 to zero-temperature behaviour at betaE(C)* much greater than 1. We determine this correction in both regimes and compare the numerical results to the numerous and controversial theoretical predictions for the strong-tunnelling limit. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2005 |
| Pages: | P01003 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Classical Monte Carlo simulations, Quantum Monte Carlo simulations |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Classical Monte Carlo simulations, Quantum Monte Carlo simulations |
| DBID source: | WOS-000227304400005, PP-9350 |
| DOI: | 10.1088/1742-5468/2005/01/P01003 |
| Nebis system number: | 004699119 |
Cluster Monte Carlo algorithms for dissipative quantum systems
,
Werner, Philipp, Troyer, Matthias,
2005
>>
| Author(s): | Werner, Philipp, Troyer, Matthias |
| Title: | Cluster Monte Carlo algorithms for dissipative quantum systems |
| Abstract: | We review efficient Monte Carlo methods for simulating quantum systems which couple to a dissipative environment. A brief introduction of the Caldeira-Leggett model and the Monte Carlo method will be followed by a detailed discussion of cluster algorithms and the treatment of long-range interactions. Dissipative quantum spins and resistively shunted Josephson junctions will be considered. |
| Published in: | Progress of theoretical physics, Supplement |
| Issue: | 160 |
| Pages: | 395 - 417 |
| ISSN: | 0375-9687 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Kyoto |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000235411000021 |
| DOI: | 10.1143/PTPS.160.395 |
| Nebis system number: | 000016191 |
Simulation results for an interacting pair of resistively shunted Josephson junctions
,
Werner, Philipp, Refael, Gil, Troyer, Matthias,
2005
>>
| Author(s): | Werner, Philipp, Refael, Gil, Troyer, Matthias |
| Title: | Simulation results for an interacting pair of resistively shunted Josephson junctions |
| Abstract: | Using a new cluster Monte Carlo algorithm, we study the phase diagram and critical properties of an interacting pair of resistively shunted Josephson junctions. This system models tunnelling between two electrodes through a small superconducting grain, and is described by a double sine-Gordon model. In accordance with theoretical predictions, we observe three different phases and crossover effects arising from an intermediate coupling fixed point. On the superconductor-to-metal phase boundary, the observed critical behaviour is within error-bars the same as in a single junction, with identical values of the critical resistance and a correlation function exponent which depends only on the strength of the Josephson coupling. We explain these critical properties on the basis of a renormalization group (RG) calculation. In addition, we propose an alternative new mean-field theory for this transition, which correctly predicts the location of the phase boundary at intermediate Josephson coupling strength. |
| Published in: | Journal of statistical mechanics: theory and experiment |
| Issue: | 12 |
| Pages: | P12003 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Dissipative systems (theory), Quantum Monte Carlo simulations, Quantum phase transitions (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Dissipative systems (theory), Quantum Monte Carlo simulations, Quantum phase transitions (theory) |
| DBID source: | WOS-000234309000011 |
| DOI: | 10.1088/1742-5468/2005/12/P12003 |
Computational complexity and fundamental limitations to fermionic quantum monte carlo simulations
,
Troyer, Matthias, Wiese, Uwe-Jens,
2005
>>
| Author(s): | Troyer, Matthias, Wiese, Uwe-Jens |
| Title: | Computational complexity and fundamental limitations to fermionic quantum monte carlo simulations |
| Abstract: | Quantum Monte Carlo simulations, while being efficient for bosons, suffer from the "negative sign problem" when applied to fermions-causing an exponential increase of the computing time with the number of particles. A polynomial time solution to the sign problem is highly desired since it would provide an unbiased and numerically exact method to simulate correlated quantum systems. Here we show that such a solution is almost certainly unattainable by proving that the sign problem is nondeterministic polynomial (NP) hard, implying that a generic solution of the sign problem would also solve all problems in the complexity class NP in polynomial time. |
| Published in: | Physical review letters |
| Volume: | 94 |
| Issue: | 17 |
| Pages: | 170201 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000228932200001, PP-9356 |
| DOI: | 10.1103/PhysRevLett.94.170201 |
| Nebis system number: | 000003868 |
Optimized ensemble Monte Carlo simulations of dense Lennard-Jones fluids
,
Trebst, Simon, Gull, Emanuel, Troyer, Matthias,
2005
>>
| Author(s): | Trebst, Simon, Gull, Emanuel, Troyer, Matthias |
| Title: | Optimized ensemble Monte Carlo simulations of dense Lennard-Jones fluids |
| Abstract: | We apply the recently developed adaptive ensemble optimization technique to simulate dense Lennard-Jones fluids and a particle-solvent model by broad-histogram Monte Carlo techniques. Equilibration of the simulated fluid is improved by sampling an optimized histogram in radial coordinates that shifts statistical weight towards the entropic barriers between the shells of the liquid. Interstitial states in the vicinity of these barriers are identified with unprecedented accuracy by sharp signatures in the quickly converging histogram and measurements of the local diffusivity. The radial distribution function and potential of mean force are calculated to high precision. |
| Published in: | The journal of chemical physics |
| Volume: | 123 |
| Issue: | 20 |
| Pages: | 204501 |
| ISSN: | 0021-9606, 1089-7690 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Melville, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000233661000044 |
| DOI: | 10.1063/1.2121709 |
| Nebis system number: | 000049290 |
Supersolids versus phase separation in two-dimensional lattice bosons
,
Sengupta, Pinaki, Pryadko, Leonid P., Alet, Fabien, Troyer, Matthias, Schmid, Guido,
2005
>>
| Author(s): | Sengupta, Pinaki, Pryadko, Leonid P., Alet, Fabien, Troyer, Matthias, Schmid, Guido |
| Title: | Supersolids versus phase separation in two-dimensional lattice bosons |
| Abstract: | We study the nature of the ground state of the two-dimensional extended boson Hubbard model on a square lattice by quantum Monte Carlo methods. We demonstrate that strong but finite on-site interaction U along with a comparable nearest-neighbor repulsion V result in a thermodynamically stable supersolid ground state for densities larger than 1/2, in contrast to fillings less than 1/2 or for very large U, where the checkerboard supersolid is unstable towards phase separation. We discuss the relevance of our results to realizations of supersolids using cold bosonic atoms in optical lattices. |
| Published in: | Physical review letters |
| Volume: | 94 |
| Issue: | 20 |
| Pages: | 207202 |
| ISSN: | 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000229398100052 |
| DOI: | 10.1103/PhysRevLett.94.207202 |
| Nebis system number: | 000003868 |
Equilibrium and dynamical properties of the Boson Hubbard model in one dimension
,
Scalettar, R.T., Batrouni, G., Denteneer, P.J.H., Muramatsu, A., Hébert, F., Rigol, M., Rousseau, V., Troyer, Matthias,
2005
>>
| Author(s): | Scalettar, R.T., Batrouni, G., Denteneer, P.J.H., Muramatsu, A., Hébert, F., Rigol, M., Rousseau, V., Troyer, Matthias |
| Title: | Equilibrium and dynamical properties of the Boson Hubbard model in one dimension |
| Abstract: | We describe quantum monte carlo simulations of the static and dynamic properties of the one dimensional boson Hubbard model, emphasizing the extent to which an external confining potential modifies the behavior. While the superfluid-Mott insulator quantum phase transition no longer exists when the system is confined, Mott and superfluid regions persist locally in the system. We construct a 'state diagram' based on the local density and compressibility profiles. Solitons present in the dynamics of the unconfined system survive the addition of a trapping potential. |
| Published in: | Journal of low temperature physics |
| Volume: | 140 |
| Issue: | 3-4 |
| Pages: | 313 - 332 |
| ISSN: | 1573-7357, 0022-2291 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Event name: | 1st International Meeting on Advances in Computational Many-Body Physics |
| Event date: | January 13-16, 2005 |
| Place: | Banff, Canada |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000231596200011 |
| DOI: | 10.1007/s10909-005-6317-6 |
| Nebis system number: | 000049402 |
Two-Step Restoration of SU(2) Symmetry in a Frustrated Ring-Exchange Magnet
,
Lauchli, A., Domenge, J.C., Lhuillier, C., Sindzingre, P., Troyer, M.,
2005
>>
| Author(s): | Lauchli, A., Domenge, J.C., Lhuillier, C., Sindzingre, P., Troyer, M. |
| Title: | Two-Step Restoration of SU(2) Symmetry in a Frustrated Ring-Exchange Magnet |
| Abstract: | We demonstrate the existence of a spin-nematic, moment-free phase in a quantum four-spin ring-exchange model on the square lattice. This unusual quantum state is created by the interplay of frustration and quantum fluctuations that lead to a partial restoration of SU(2) symmetry when going from a four-sublattice orthogonal biaxial Neel order to this exotic uniaxial magnet. A further increase of frustrationdrives a transition to a fully gapped SU(2) symmetric valence bond crystal. |
| Published in: | Physical review letters |
| Volume: | 95 |
| Issue: | 13 |
| Pages: | 137206 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000232060100052, PP-9361 |
| DOI: | 10.1103/PhysRevLett.95.137206 |
| Nebis system number: | 000003868 |
Symmetry projection schemes for Gaussian Monte Carlo methods
,
Assaad, F.F., Werner, P., Corboz, P., Gull, E., Troyer, Matthias,
2005
>>
| Author(s): | Assaad, F.F., Werner, P., Corboz, P., Gull, E., Troyer, Matthias |
| Title: | Symmetry projection schemes for Gaussian Monte Carlo methods |
| Abstract: | A sign-free Monte Carlo method for the Hubbard model has recently been proposed by Corney and Drummond. High-precision measurements on small clusters show that ground-state correlation functions are not correctly reproduced. We argue that the origin of this mismatch lies in the fact that the low-temperature density matrix does not have the symmetries of the Hamiltonian. Here we show that supplementing the algorithm with symmetry projection schemes provides reliable and accurate estimates of ground-state properties. |
| Published in: | Physical review. B, Condensed matter and materials physics |
| Volume: | 72 |
| Issue: | 22 |
| Pages: | 224518 |
| ISSN: | 0163-1829, 1098-0121, 0556-2805, 1550-235X |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000234335600093 |
| DOI: | 10.1103/PhysRevB.72.224518 |
| Nebis system number: | 001888782 |
Generalized directed loop method for quantum Monte Carlo simulations
,
Alet, Fabien, Wessel, Stefan, Troyer, Matthias,
2005
>>
| Author(s): | Alet, Fabien, Wessel, Stefan, Troyer, Matthias |
| Title: | Generalized directed loop method for quantum Monte Carlo simulations |
| Abstract: | Efficient quantum Monte Carlo update schemes called directed loops have recently been proposed, which improve the efficiency of simulations of quantum lattice models. We propose to generalize the detailed balance equations at the local level during the loop construction by accounting for the matrix elements of the operators associated with open world-line segments. Using linear programming techniques to solve the generalized equations, we look for optimal construction schemes for directed loops. This also allows for an extension of the directed loop scheme to general lattice models, such as high-spin or bosonic models. The resulting algorithms are bounce free in larger regions of parameter space than the original directed loop algorithm. The generalized directed loop method is applied to the magnetization process of spin chains in order to compare its efficiency to that of previous directed loop schemes. In contrast to general expectations, we find that minimizing bounces alone does not always lead to more efficient algorithms in terms of autocorrelations of physical observables, because of the nonuniqueness of the bounce-free solutions. We therefore propose different general strategies to further minimize autocorrelations, which can be used as supplementary requirements in any directed loop scheme. We show by calculating autocorrelation times for different observables that such strategies indeed lead to improved efficiency; however, we find that the optimal strategy depends not only on the model parameters but also on the observable of interest. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 71 |
| Issue: | 3 |
| Pages: | 036706-1 - 036706-16 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Physik und Astronomie|Physics and Astronomy |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000228818200156, PP-731 |
| DOI: | 10.1103/PhysRevE.71.036706 |
| Nebis system number: | 004109079 |
Interacting classical dimers on the square lattice
,
Alet, Fabien, Jacobsen, Jesper Lykke, Misguich, Grégoire, Pasquier, Vincent, Mila, Frédéric, Troyer, Matthias,
2005
>>
| Author(s): | Alet, Fabien, Jacobsen, Jesper Lykke, Misguich, Grégoire, Pasquier, Vincent, Mila, Frédéric, Troyer, Matthias |
| Title: | Interacting classical dimers on the square lattice |
| Abstract: | We study a model of close-packed dimers on the square lattice with a nearest neighbor interaction between parallel dimers. This model corresponds to the classical limit of quantum dimer models [D. S. Rokhsar and S. A. Kivelson, Phys. Rev. Lett. 61, 2376 (1988)]. By means of Monte Carlo and transfer matrix calculations, we show that this system undergoes a Kosterlitz-Thouless transition separating a low temperature ordered phase where dimers are aligned in columns from a high temperature critical phase with continuously varying exponents. This is understood by constructing the corresponding Coulomb gas, whose coupling constant is computed numerically. We also discuss doped models and implications on the finite-temperature phase diagram of quantum dimer models. |
| Published in: | Physical review letters |
| Volume: | 94 |
| Issue: | 23 |
| Pages: | 235702 |
| Publication date / Date received: | 2005-01-01 |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000229858100038, PP-9363 |
| DOI: | 10.1103/PhysRevLett.94.235702 |
| Nebis system number: | 000003868 |
Quantum Monte Carlo simulations of confined bosonic atoms in optical lattices
,
Wessel, Stefan, Alet, Fabien, Troyer, Matthias, Batrouni, G. George,
2004
>>
| Author(s): | Wessel, Stefan, Alet, Fabien, Troyer, Matthias, Batrouni, G. George |
| Title: | Quantum Monte Carlo simulations of confined bosonic atoms in optical lattices |
| Abstract: | We study properties of ultracold bosonic atoms in one-, two-, and three-dimensional optical lattices by large scale quantum Monte Carlo simulations of the Bose-Hubbard model in parabolic confining potentials. Our results indicate that local properties of the atoms can be accessed by probing the system's response to local potential perturbations. Furthermore, we show how the formation of Mott insulating regions is reflected in the momentum distribution of the atoms, amenable to experimental detection. We disprove previous claims concerning the relevance of fine structure in the momentum distribution function. Furthermore, we discuss limitations of local density approximations for confined systems, and demonstrate the absence of quantum criticality due to the inhomogenous potential. Instead, we show that quantum critical behavior can be observed in flat confining potentials. Our results indicate that the experimental detection of the Mott transition in moderately sized optical lattices would be significantly eased in flat confinement potentials. |
| Published in: | Physical review. A, Atomic, molecular and optical physics |
| Volume: | 70 |
| Issue: | 5 |
| Pages: | 053615 |
| ISSN: | 1050-2947, 1094-1622 |
| Publication date / Date received: | 2004-01-01 |
| Publication status: | Woodbury, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000225479000119 |
| DOI: | 10.1103/PhysRevA.70.053615 |
| Nebis system number: | 000619853 |
Optimizing the ensemble for equilibration in broad-histogram Monte Carlo simulations
,
Trebst, Simon, Huse, David A., Troyer, Matthias,
2004
>>
| Author(s): | Trebst, Simon, Huse, David A., Troyer, Matthias |
| Title: | Optimizing the ensemble for equilibration in broad-histogram Monte Carlo simulations |
| Abstract: | We present an adaptive algorithm which optimizes the statistical-mechanical ensemble in a generalized broad-histogram Monte Carlo simulation to maximize the system's rate of round trips in total energy. The scaling of the mean round-trip time from the ground state to the maximum entropy state for this local-update method is found to be O([N ln N](2)) for both the ferromagnetic and the fully frustrated, two-dimensional Ising model with N spins. Our algorithm thereby substantially outperforms flat-histogram methods such as the Wang-Landau algorithm. |
| Published in: | Physical review E, Statistical, nonlinear, and soft matter physics |
| Volume: | 70 |
| Issue: | 4 |
| Pages: | 046701 |
| ISSN: | 1539-3755, 1063-651X, 1095-3787, 1550-2376 |
| Publication date / Date received: | 2004-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000225689600114 |
| DOI: | 10.1103/PhysRevE.70.046701 |
| Nebis system number: | 004109079 |
Computational Complexity and Simulation of Rare Events of Ising Spin Glasses
,
Pelikan, Martin, Ocenasek, Jiri, Trebst, Simon, Troyer, Matthias, Alet, Fabien,
2004
>>
| Author(s): | Pelikan, Martin, Ocenasek, Jiri, Trebst, Simon, Troyer, Matthias, Alet, Fabien |
| Title: | Computational Complexity and Simulation of Rare Events of Ising Spin Glasses |
| Abstract: | We discuss the computational complexity of random 2D Ising spin glasses, which represent an interesting class of constraint satisfaction problems for black box optimization. Two extremal cases are considered: (1) the +/-J spin glass, and (2) the Gaussian spin glass. We also study a smooth transition between these two extremal cases. The computational complexity of all studied spin glass systems is found to be dominated by rare events of extremely hard spin glass samples. We show that complexity of all studied spin glass systems is closely related to Frechet extremal value distribution. In a hybrid algorithm that combines the hierarchical Bayesian optimization algorithm (hBOA) with a deterministic bit-flip hill climber, the number of steps performed by both the global searcher (hBOA) and the local searcher follow Frechet distributions. Nonetheless, unlike in methods based purely on local search, the parameters of these distributions confirm good scalability of hBOA with local search. We further argue that standard performance measures for optimization algorithms-such as the average number of evaluations until convergence-can be misleading. Finally, our results indicate that for highly multimodal constraint satisfaction problems, such as Ising spin glasses, recombination-based search can provide qualitatively better results than mutation-based search. |
| Book title: | Genetic and evolutionary computation - GECCO 2004 |
| Volume: | 3103 |
| Pages: | 36 - 47 |
| ISBN: | 3-540-22343-6 |
| Publication date / Date received: | 2004-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Event name: | 6th Annual Genetic and Evolutionary Computation Conference (GECCO 2004) |
| Event date: | June 26-30, 2004 |
| Place: | Seattle, WA, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000225040600004 |
| DOI: | 10.1007/978-3-540-24855-2_4 |
| Nebis system number: | 004830707 |
Dynamics of the Wang-Landau algorithm and complexity of rare events for the three-dimensional bimodal Ising spin glass
,
Alder, Simon, Trebst, Simon, Hartmann, Alexander K., Troyer, Matthias,
2004
>>
| Author(s): | Alder, Simon, Trebst, Simon, Hartmann, Alexander K., Troyer, Matthias |
| Title: | Dynamics of the Wang-Landau algorithm and complexity of rare events for the three-dimensional bimodal Ising spin glass |
| Abstract: | We investigate the performance of flat-histogram methods based on a multicanonical ensemble and the Wang-Landau algorithm for the three-dimensional +/-J spin glass by measuring round-trip times in the energy range between the zero-temperature ground state and the state of highest energy. Strong sample-to-sample variations are found for fixed system size and the distribution of round-trip times follows a fat-tailed Frechet extremal value distribution. Rare events in the fat tails of these distributions corresponding to extremely slowly equilibrating spin glass realizations dominate the calculations of statistical averages. While the typical round-trip times scale exponentially as expected for this NP-hard problem, we find that the average round-trip time is no longer well defined for systems with N greater than or equal to 8(3) spins. We relate the round-trip times for multicanonical sampling to intrinsic properties of the energy landscape and compare with the numerical effort needed by the genetic cluster-exact approximation to calculate the exact ground-state energies. For systems with N greater than or equal to 8(3) spins the simulation of these rare events becomes increasingly hard. For N greater than or equal to 14(3) there are samples where the Wang-Landau algorithm fails to find the true ground state within reasonable simulation times. We expect similar behaviour for other algorithms based on multicanonical sampling. |
| Published in: | Journal of statistical mechanics |
| Volume: | 2004 |
| Issue: | 7 |
| Pages: | P07008 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2004-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | classical Monte Carlo simulations, energy landscapes (theory), spin glasses (theory) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | classical Monte Carlo simulations, energy landscapes (theory), spin glasses (theory) |
| DBID source: | WOS-000227256000008 |
| DOI: | 10.1088/1742-5468/2004/07/P07008 |
| Nebis system number: | 004699119 |
Wichtiger Hinweis:
Diese Website wird in älteren Versionen von Netscape ohne
graphische Elemente dargestellt. Die Funktionalität der
Website ist aber trotzdem gewährleistet. Wenn Sie diese
Website regelmässig benutzen, empfehlen wir Ihnen, auf
Ihrem Computer einen aktuellen Browser zu installieren. Weitere
Informationen finden Sie auf
folgender
Seite.
Important Note:
The content in this site is accessible to any browser or
Internet device, however, some graphics will display correctly
only in the newer versions of Netscape. To get the most out of
our site we suggest you upgrade to a newer browser.
More
information
